1. An image forming apparatus, comprising: a plurality of image forming devices including a developing device that develops an electrostatic latent image formed on an image bearing member to form a toner image, and a transferring device that transfers the toner image developed by the developing device onto any of a conveyance member and a transfer material on the conveyance member, for each of a plurality of colors; an exposure unit irradiating the image bearing member with a laser beam to form the electrostatic latent image on the image bearing member; a detector detecting a toner image for detection that is a toner image for detecting a positional deviation of each color transferred onto the conveyance member by the transferring device; and a control device detecting and correcting the positional deviation of each color based on a detection result of the toner image for detection detected by the detector, wherein the control device allows one of said plurality of image forming devices to form a toner image for detection with one color between pages in a print job including plural pages of images, and corrects timing at which the exposure unit emits the laser beam based on a time between timing pertaining to start of forming the toner image for detection and timing on which the detector detects the toner image for detection.