A multi-beam emitting device which emits a multi-beam having a substantially equal wavelength and including a substrate and a plurality of laser beam emitting portions formed on the substrate, each of the laser beam emitting portions having an N type electrode layer, a P type electrode layer, and an active layer interposed between the N type and P type electrode layers. Each of the active layers is arranged such that a plane in which each active layer extends is substantially parallel to an upper surface of the substrate, and wherein the active layers are separated by a predetermined distance from each other in a direction following the upper surface of the substrate and simultaneously separated by a predetermined distance in a direction normal to the upper surface of the substrate. A light scanning unit is provided including the emitting device, a light deflection unit deflecting light beams emitted from the laser emitting device, and a scanning optical system scanning each of the light beams deflected by the light deflection unit in a sub-scanning direction to be separated by a predetermined pitch and parallel to each other.