The optical scanning device includes a deflector 22 for deflecting plural laser beams in batch, first and second ftheta lenses 24, 25 for converting the laser beams from the deflector 22 into uniform speed linear motion, reflection mirrors 23a to 23g for reflecting the laser beams from the first and second ftheta lenses 24, 25, photoreceptor drums 2a, 2b, 2c, 2d on which latent images are formed by laser beams, and third ftheta lenses 26a to 26d for focusing the laser beams reflected by the reflection mirrors 23a to 23g and guiding onto the photoreceptor drums 2a, 2b, 2c, 2d. The laser beam 9a reflected by the reflection mirror 23 remotest from the deflector 23 is the laser beam for forming a yellow image.
Optical scanning device used in a tandem system color image forming apparatus