diff --git a/toonz/sources/CMakeLists.txt b/toonz/sources/CMakeLists.txt
index fe4f74e..3e2316b 100644
--- a/toonz/sources/CMakeLists.txt
+++ b/toonz/sources/CMakeLists.txt
@@ -120,7 +120,7 @@ set(CMAKE_INCLUDE_CURRENT_DIR ON)
 if(APPLE)
     set(CMAKE_MACOSX_RPATH ON)
     set(CMAKE_SKIP_BUILD_RPATH FALSE)
-    set(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE) 
+    set(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)
     set(CMAKE_INSTALL_RPATH ${QT_LIB_PATH})
     set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
     list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${QT_LIB_PATH}" isSystemDir)
@@ -451,6 +451,11 @@ add_subdirectory(tcleanupper)
 add_subdirectory(tcomposer)
 add_subdirectory(tconverter)
 add_subdirectory(toonzfarm)
+
+if(APPLE)
+    add_subdirectory(mousedragfilter)
+endif()
+
 if((PLATFORM EQUAL 32) AND (WIN32 OR APPLE))
     add_subdirectory(t32bitsrv)
 endif()
diff --git a/toonz/sources/mousedragfilter/CMakeLists.txt b/toonz/sources/mousedragfilter/CMakeLists.txt
new file mode 100644
index 0000000..5158770
--- /dev/null
+++ b/toonz/sources/mousedragfilter/CMakeLists.txt
@@ -0,0 +1,10 @@
+if(APPLE)
+    cmake_minimum_required(VERSION 2.8.11)
+    project(MouseDragFilter)
+
+    include_directories(.)
+    find_library(FOUNDATION_LIBRARY NAMES foundation)
+    find_library(CG_LIBRARY NAMES CoreGraphics)
+    add_library(mousedragfilter mousedragfilter.mm mousedragfilter.h)
+    target_link_libraries(mousedragfilter ${CG_LIBRARY} ${FOUNDATION_LIBRARY})
+endif()
diff --git a/toonz/sources/mousedragfilter/mousedragfilter.h b/toonz/sources/mousedragfilter/mousedragfilter.h
new file mode 100644
index 0000000..1f39281
--- /dev/null
+++ b/toonz/sources/mousedragfilter/mousedragfilter.h
@@ -0,0 +1,6 @@
+#pragma once
+bool IsLeftMouseDragged(void *);
+bool IsLeftMouseDown(void *);
+bool IsLeftMouseUp(void *);
+void MonitorNSMouseEvent(void *);
+void SendLeftMousePressEvent();
diff --git a/toonz/sources/mousedragfilter/mousedragfilter.mm b/toonz/sources/mousedragfilter/mousedragfilter.mm
new file mode 100644
index 0000000..a4a138f
--- /dev/null
+++ b/toonz/sources/mousedragfilter/mousedragfilter.mm
@@ -0,0 +1,61 @@
+#include <iostream>
+#include "mousedragfilter.h"
+#import <AppKit/AppKit.h>
+#import <CoreGraphics/CoreGraphics.h>
+
+
+bool IsLeftMouseDown(void *message){
+  NSEvent * event = (NSEvent*)message;
+  if([event type] == NSLeftMouseDown){
+    return true;
+  }
+  return false;
+}
+
+
+bool IsLeftMouseUp(void *message){
+  NSEvent * event = (NSEvent*)message;
+  if([event type] == NSLeftMouseUp){
+    return true;
+  }
+  return false;
+}
+
+
+bool IsLeftMouseDragged(void *message){
+  NSEvent * event = (NSEvent*)message;
+  if([event type] == NSLeftMouseDragged){
+    return true;
+  }
+  return false;
+}
+
+
+void MonitorNSMouseEvent(void *message){
+  NSEvent * event = (NSEvent*)message;
+  switch ([event type]) {
+  case NSLeftMouseDown:
+    std::cout << "Lv" << std::endl; break;
+  case NSLeftMouseUp:
+    std::cout << "L^" << std::endl; break;
+  case NSRightMouseDown:
+    std::cout << "Rv" << std::endl; break;
+  case NSRightMouseUp:
+    std::cout << "R^" << std::endl; break;
+  case NSOtherMouseDown:
+    std::cout << [event buttonNumber] << "v" << std::endl; break;
+  case NSOtherMouseUp:
+    std::cout << [event buttonNumber] << "^" << std::endl; break;
+  default:
+    break;
+  }
+}
+
+
+void SendLeftMousePressEvent(){
+  CGEventRef event = CGEventCreate(NULL);
+  CGPoint location = CGEventGetLocation(event);
+  CFRelease(event);
+  CGEventRef mouseDown = CGEventCreateMouseEvent(NULL, kCGEventLeftMouseDown, location, kCGMouseButtonLeft);
+  CGEventPost(kCGHIDEventTap, mouseDown);
+}
diff --git a/toonz/sources/toonz/CMakeLists.txt b/toonz/sources/toonz/CMakeLists.txt
index 12c7927..c3d76c8 100644
--- a/toonz/sources/toonz/CMakeLists.txt
+++ b/toonz/sources/toonz/CMakeLists.txt
@@ -357,6 +357,12 @@ include_directories(
     ../../sources/toonzqt
 )
 
+if(APPLE)
+    include_directories(../../sources/mousedragfilter)
+endif()
+
+
+
 if(WIN32)
     if(PLATFORM EQUAL 32)
         include_directories(
@@ -379,7 +385,9 @@ elseif(APPLE)
     # 変なところにライブラリ生成するカスども
     set(EXTRA_LIBS ${EXTRA_LIBS} "$<TARGET_FILE:tnzstdfx>" "$<TARGET_FILE:tfarm>")
 
-    target_link_libraries(OpenToonz_${VERSION} Qt5::Core Qt5::Gui Qt5::Network Qt5::OpenGL Qt5::Svg Qt5::Xml Qt5::Script Qt5::Widgets Qt5::PrintSupport Qt5::Multimedia ${GL_LIB} ${GLUT_LIB} ${COCOA_LIB} ${EXTRA_LIBS})
+
+    target_link_libraries(OpenToonz_${VERSION} Qt5::Core Qt5::Gui Qt5::Network Qt5::OpenGL Qt5::Svg Qt5::Xml Qt5::Script Qt5::Widgets Qt5::PrintSupport Qt5::Multimedia ${GL_LIB} ${GLUT_LIB} ${COCOA_LIB} ${EXTRA_LIBS} mousedragfilter)
+
 elseif(UNIX)
     _find_toonz_library(EXTRA_LIBS "tnzcore;tnzbase;toonzlib;colorfx;tnzext;image;sound;toonzqt;tnztools")
 
@@ -509,4 +517,3 @@ exec \$OPENTOONZ_BASE/bin/OpenToonz_${VERSION} \"\$@\"
     )
 
 endif()
-
diff --git a/toonz/sources/toonz/main.cpp b/toonz/sources/toonz/main.cpp
index 586d4e6..00dd059 100644
--- a/toonz/sources/toonz/main.cpp
+++ b/toonz/sources/toonz/main.cpp
@@ -71,6 +71,8 @@
 
 // Qt includes
 #include <QApplication>
+#include <QAbstractEventDispatcher>
+#include <QAbstractNativeEventFilter>
 #include <QSplashScreen>
 #include <QGLPixelBuffer>
 #include <QTranslator>
@@ -263,6 +265,42 @@ int main(int argc, char *argv[]) {
 
   QApplication a(argc, argv);
 
+#ifdef MACOSX
+// This workaround is to avoid missing left button problem on Qt5.6.0.
+// To invalidate m_rightButtonClicked in Qt/qnsview.mm, sending NSLeftButtonDown
+// event
+// before NSLeftMouseDragged event propagated to QApplication.
+// See more details in ../mousedragfilter/mousedragfilter.mm.
+
+#include "mousedragfilter.h"
+
+  class OSXMouseDragFilter final : public QAbstractNativeEventFilter {
+    bool leftButtonPressed = false;
+
+  public:
+    bool nativeEventFilter(const QByteArray &eventType, void *message,
+                           long *) Q_DECL_OVERRIDE {
+      if (IsLeftMouseDown(message)) {
+        leftButtonPressed = true;
+      }
+      if (IsLeftMouseUp(message)) {
+        leftButtonPressed = false;
+      }
+
+      if (eventType == "mac_generic_NSEvent") {
+        if (IsLeftMouseDragged(message) && !leftButtonPressed) {
+          std::cout << "force mouse press event" << std::endl;
+          SendLeftMousePressEvent();
+          return true;
+        }
+      }
+      return false;
+    }
+  };
+
+  a.installNativeEventFilter(new OSXMouseDragFilter);
+#endif
+
 #ifdef Q_OS_WIN
   //	Since currently OpenToonz does not work with OpenGL of software or
   // angle,
@@ -483,7 +521,7 @@ int main(int argc, char *argv[]) {
   TApp::instance()->init();
 
 // iwsw commented out temporarily
-#if 0 
+#if 0
   QStringList monitorNames;
   /*-- 接続モニタがPVM-2541の場合のみLUTを読み込む --*/
   if (Preferences::instance()->isDoColorCorrectionByUsing3DLutEnabled())