An image forming apparatus includes plural laser light sources, a polygonal mirror that scans plural laser beams from the plural laser light sources, and a multiplexing member that combines the plural laser beams scanned by the polygonal mirror. The polygonal mirror is disposed above or below the multiplexing member, and the extension of the rotation axis of the polygonal mirror passes through the multiplexing member. When configured in this manner, it is possible to reduce the apparatus size and speckle noises caused by the plural laser beams.