To suppress generation of phase deviation between rotating members and offset ghost caused by ununiformity of thickness of a timing belt generated through the rotating member rotating by being brought into contact with the back face of the timing belt while cost reduction of the linking system of the timing belt is kept.

Thickness of the belt is made uniform by abrading the back face of the timing belt 320 hung around through a means 322 for adjusting phases between drums and polarization pulleys 344 as rotating members rotating by being brought into contact with the back face of the timing belt between a drum driving pulley 336 for a printing drum 308 and a drum driving pulley 338 for a printing drum 310.