To exactly align an optical axis of a light source with an optical axis of the post-stage even after the light source is attached to base material.

A light source device 101 includes: the light sources 101R, 101G and 101B; cooling fins 1,011 attached to the light sources 101R, 101G and 101B; the base material 1,010 performing positioning in the optical axis direction of the light sources 101R, 101G and 101B; a pressing plate 1,020 holding and fixing the cooling fin 1,011 between the base material 1,010 and the pressing plate 1,020; a first eccentric cam whose rotary shaft is inserted in the base material 1,010 and whose cam abuts on the end of the cooling fin 1,011 so as to adjust the position in the direction of a first axis out of two axes orthogonal to the optical axis of the light source; and a second eccentric cam whose rotary shaft is inserted in the cooling fin 1,011 and whose cam abuts on the end of the pressing plate 1,020 so as to adjust the position in the direction of a second axis out of two axes orthogonal to the optical axis of the light source.