An image forming apparatus including: an image forming section which forms an image on a photosensitive drum based on a reference signal which being an image write control signal of a predetermined cycle; a measuring section which detects a rotational velocity of the photosensitive drum and measures a velocity fluctuation distribution in time period of one rotation of the drum; a storage section which stores a correction value as a correction data table for each type of recording sheets, wherein the correction value is obtained based on the velocity fluctuation distribution; and a control section which corrects the cycle of the reference signal by referring the correction data table corresponding to a selected type of recording sheets, and controls the image forming section to form the image on the photosensitive drum based on the reference signal with the corrected cycle.