Light source device and projection type display unit to which the device is applied

A light emitted from a semiconductor light emitting device array having a plurality of semiconductor light emitting devices arranged two-dimensionally on a substrate is converged by a condensing lens. In a light guide, a mirror surface is formed from a light incidence port to a light emission port along an inner wall surface. The semiconductor light emitting device array and the condensing lens are arranged in that order toward the light emission port inside the light incidence port of the light guide. A part of the inner wall surface of the light guide is narrowed down substantially along a condensing angle of the condensing lens. The light guide includes parallel inner wall surfaces facing each other, following a portion obtained by narrowing down a part of the inner wall surface, in order to emit the light (each color light) converged by the condensing lens while repeatedly reflecting the light on the mirror surface.