An image forming apparatus forms an image by laser beams from a plurality of lasers. The image forming apparatus includes a light amount control circuit that detects displacement in a sub-scanning direction of the main scanning line of a laser beam from the predetermined laser, from a reference position. The apparatus decides an allotted amount of light for each of the plurality of lasers in accordance with the detected displacement and controls to drive each of the plurality of lasers in accordance with the decided allotted amount of light for each laser.