An optical unit includes: a heat sink that radiates heat from a light source; and a base portion including a reflector mounting section, a lens mounting section and a connecting section connecting the reflector mounting section and the lens mounting section. The base portion is configured such that the light from the light source is reflected by a reflector mounted onto the reflector mounting section and is incident onto a projection lens mounted onto the lens mounting section. The heat sink is exposed to a space surrounded by the lens mounting section, the connecting section and the reflector mounting section.