Thank to Arno Duvenhage and Tom for their answers. Here are steps who worked for me in Qt 5.2.1 and Visual Studio 2012 and 2015:
Install QT Add In (for visual studio 2015 is in still in beta, but works fully for me).
Right click the project, select "Unload project".
Add add the Qt4VSv1.0
entry into the
tag.
Select load project.
Select "Convert project to Qt Add-in project" in "Qt 5" menu.
Almost done. Go to Qt project settings and Qt option in the Qt menu to set details.
In your project properties Linker\Additional Library Directories\ might need to add $(QTDIR)\lib
In your project properties C++\Additional Include Directories\ might need to add $(QTDIR)\include
In each of your classes derived from Q_OBJECT, delete the Q_OBJECT macro, save the file, return the Q_OBJECT macro (Ctrl+Z), and save again. It adds the 'moc' files to your generated files folder.
Set your project as startup project.