The index of refraction of a light guide (6) for transmitting light outputted from a primary light source (1) is ng, and the light guide (6) has a light input end face (9), a light output surface from which the transmitted light is outputted, and a back surface opposed to the light output surface. A leaky ray modulator (8) is provided to at least either the light output surface or the back surface. The leaky ray modulator (8) has a composite layer (50) provided on the light output surface or the back surface and composed of first refractive index regions (3) having a refractive index n1 (ngn1) and second refractive index regions (4) having a refractive index n2 (n2n1) and a third refractive index layer (5) provided on the composite layer (50) and having a refractive index n3 (n3n1). A reflecting plate (7) is provided adjacent to the back surface of the light guide (6).