To provide a light source device capable of outputting a luminous flux in high efficiency by enlarging the amount of luminous flux per unit area of a light-emitting section.

The light source device is provided with a first solid light-emitting element 2 to emit primary light; a first phosphor film 3 which absorbs the primary light and emits secondary light; a prism 1 which has an incident face 11 arranged along the first phosphor film 3 through the air, an inclined face 12 which faces inclined to the incident face 11, two perpendicular faces which are opposed to each other mutually in parallel perpendicular to the incident face 11 and the inclined face 12, an emitting face 13 which continues from the incident face 11, the inclined face 12, and the two perpendicular faces on the side where the interval between the incident face 11 and the inclined face 12 is widened, and has an area smaller than that of the first phosphor film, and an included angle face 14 which is opposed to the emitting face 13 in parallel; and a first secondary light reflecting film 4 which is arranged between the first solid light-emitting element 2 and the first phosphor film 3 and transmits the primary light and reflects the secondary light.