A light source device includes a plurality of light sources each comprising a semiconductor laser device, a mounting body to which the plurality of light sources is attached, and at least one heat conducting member. The mounting body has a front surface to be a light emitting side and a rear surface opposite to the front surface. The rear surface has at least one first surface portion. Terminals of at least one of the plurality of light sources protrude from each of the at least one first surface portion. The rear surface has at least one second surface portion which is closer to the front surface than any one of the at least one first surface portion. Each of the at least one heat conducting member is in contact with corresponding one of the at least one second surface portion.