the present invention provides an image forming apparatus including : a rotating body that holds recording medias on a circumferential surface ; an image forming section that forms an image ; a generating section that generates a pulse and a reference pulse ; a measuring section that measures the number of pulses ; a computing section that each time when predetermined number of pulses from generation of the reference pulse has been measured , divides a pulse width of a pulse before predetermined number of pulses by a first value to compute a pulse division time ; and a controlling section that each time when predetermined number of pulses are measured from generation of the reference pulse , multiplies the pulse division time by a second predetermined value , thereby obtaining a forming start time , and that controls to start image formation when the forming start time has elapsed from the measurement of predetermined number of pulses .