A multi-beam scanning device including a multi-beam light source including plural laser diode arrays emitting plural laser beams and at least one coupling lens; a deflector configured to deflect the plural laser beams; an optical system configured to guide the deflected plural laser beams to an image forming surface; a body configured to contain the multi-beam light source, deflector and scanning optical system; and an adjustment member located between the body and the multi-beam light source and configured to adjust the beam pitch of the plural laser beams in the sub-scanning direction. An image forming apparatus including an image bearing member, the above-mentioned scanning device and an image forming device.