A color laser printer producing a color image using a single laser scanning unit includes a lighting unit including first and second laser diodes emitting beams of one polarization, a polarization prism transmitting or reflecting incident beams depending on a direction of polarization, and third and fourth laser diodes disposed in a different direction from the first and second laser diodes with respect to the polarization prism, a rotary polygon mirror that reflects the beam emitted along the same path from the lighting unit, an f-θ lens that focuses the beam reflected by the rotary polygon mirror, first and second polarization beam splitters, each of which transmits or reflects the beam passing through the f-θ lens depending on the direction of the polarization, and first through fourth photoconductive units on which the beams reflected and transmitted through the first and second polarization beam splitters are incident. In the color laser printer, lengths of optical paths between the f-θ lens and each of the first through fourth photoconductive units are equal. The color laser printer is constructed such that a plurality of light sources emitting the beams of one polarization are arranged separately and the beams emitted from the light sources are combined by the polarization prism to enter the f-θ lens, thereby reducing a thickness of the f-θ lens.