So I've chosen a font by

System Settings -> Application Appearance -> Fonts

And there I've adjusted all fonts to be of 14th size. And also checked "Use my KDE fonts..." in Gtk+ appearance. I've also did the same using

kdesudo systemsettings

But still some fonts are tiny! It's not the 14th size!

Edit 2:

I thought it might be one of Gnome font settings. So I've increased all fonts in

gnome-tweak-tool

sudo gnome-tweak-tool

gconf-editor

sudo gconf-editor

No help!

Edit:

Ubuntu tweak also gives no help (note the tiny fonts!):

Edit:

It looks like the problem is with gtk3: when I compile emacs 24.0.92 with gtk3 - i get small menu fonts. When I do the same with a default gtk2 - everything is all right.