A light source apparatus comprising: a light source unit that includes a plurality of source sets, each source set comprising a laser and a coupling lens corresponding to the laser, the source sets being arranged around the circumference of a circle; a reflecting unit placed within the circle and provided with a plurality of reflecting surfaces corresponding to the source sets and forming a cone shape, the light beam emitted by each of the lasers being directed on to the corresponding reflecting surface via the corresponding coupling lens; a support member on which the lasers and the coupling lenses of the source sets are fixed, wherein the lasers and the coupling lenses of the source sets are positioned such that optical axes of the light beams emitted by the lasers are directed in a thickness direction of the support member; a plurality of reflecting mirrors provided to change the optical paths of the light beams emitted by the respective lasers and passed through the coupling lenses toward the respective reflecting surfaces of the reflecting unit; and a radiation member provided at a surface of the support member opposite to the side where the light paths of the light beams emitted by the lasers of the sets are formed, and including a flat surface formed at a center portion, and plural fins projecting in a radial direction; the apparatus being characterized in that: the radiation member further includes a guide surface which is provided at the outer side, in a radial direction, of the flat surface and is concave from the flat surface; and the plural fins project from the guide surface, wherein those of the plural fins which are located at positions of the support member on which the lasers are fixed are provided with opening portions, said opening portions being configured to accept the corresponding laser fixed on the support member. a light source unit that includes a plurality of source sets, each source set comprising a laser and a coupling lens corresponding to the laser, the source sets being arranged around the circumference of a circle; a reflecting unit placed within the circle and provided with a plurality of reflecting surfaces corresponding to the source sets and forming a cone shape, the light beam emitted by each of the lasers being directed on to the corresponding reflecting surface via the corresponding coupling lens; a support member on which the lasers and the coupling lenses of the source sets are fixed, wherein the lasers and the coupling lenses of the source sets are positioned such that optical axes of the light beams emitted by the lasers are directed in a thickness direction of the support member; a plurality of reflecting mirrors provided to change the optical paths of the light beams emitted by the respective lasers and passed through the coupling lenses toward the respective reflecting surfaces of the reflecting unit; and a radiation member provided at a surface of the support member opposite to the side where the light paths of the light beams emitted by the lasers of the sets are formed, and including a flat surface formed at a center portion, and plural fins projecting in a radial direction; the apparatus being characterized in that: the radiation member further includes a guide surface which is provided at the outer side, in a radial direction, of the flat surface and is concave from the flat surface; and the plural fins project from the guide surface, wherein those of the plural fins which are located at positions of the support member on which the lasers are fixed are provided with opening portions, said opening portions being configured to accept the corresponding laser fixed on the support member. the radiation member further includes a guide surface which is provided at the outer side, in a radial direction, of the flat surface and is concave from the flat surface; and the plural fins project from the guide surface, wherein those of the plural fins which are located at positions of the support member on which the lasers are fixed are provided with opening portions, said opening portions being configured to accept the corresponding laser fixed on the support member.