A
light source unit capable of considerably reducing the size of a vehicular lamp. An LED is mounted on an
optical axis extending in the longitudinal direction of the vehicle with its light output directed upward, and a reflector is provided above the LED having a first reflecting surface for collecting the light emitted by the LED and reflecting the light generally in the direction of the
optical axis Ax. The reflector is formed by a reflective
coating formed on the surface of a translucent block covering the LED. Consequently, the size of the reflector can be considerably reduced as compared with reflectors employed in conventional vehicular lamps. Moreover, since the LED used as a
light source emits little heat, the reflector can be designed without having to take into account the influence of heat generated by the
light source. Furthermore, the LED can be treated substantially as a
point light source so that proper reflection control can be carried out even if the size of the reflector is reduced. By mounting the LED so that its light output is directed substantially orthogonal to the
optical axis Ax, moreover, it is possible to effectively utilize most of the light emitted by the LED and reflected by the first reflecting surface.