The invention provides an image forming apparatus comprising: an electrophotographic photoreceptor having a conductive substrate and a photosensitive layer provided on the conductive substrate; a charging unit for charging the electrophotographic photoreceptor; an exposure unit for exposing the charged electrophotographic photoreceptor to light thereby forming an electrostatic latent image; a developing unit for developing the electrostatic latent image with toner thereby forming a toner image; and a transfer unit for transferring the toner image from the electrophotographic photoreceptor to a transferred image-receiving medium, wherein said exposure unit is a multi beam exposure unit which has a surface emitting laser array and which carries out the electrostatic latent image formation by scanning the electrophotographic photoreceptor with eight or more light beams; and wherein said electrophotographic photoreceptor gives a quantum efficiency of 0.3 or higher when the electrophotographic photoreceptor is charged to a charged potential absolute value of 500 V and then irradiated with a monochromatic light of the same wavelength as that of said light beams to decay the charged potential absolute value to 250 V.