The image forming apparatus includes: a paper feed unit; a print unit; a registration roller; a sheet leading end sensor provided downstream, in a transport direction of the recording paper, of the registration roller; a time measuring unit for measuring a time from a start point of transportation of the recording paper by the registration roller to a point of detection of the leading end of the recording paper by the sheet leading end sensor; a memory unit for storing a reference image forming time and a reference time; a print control unit; and an arithmetic unit for obtaining a difference between the reference time and the time detected by the time measuring unit. The print control unit adjusts the length of the image forming period in accordance with the adjusted image forming time determined based on the difference obtained by the arithmetic unit and the reference image forming time.