A lamp unit for a vehicle incorporating a reflector disposed on the inside of a case-shape lamp body; a bulb disposed in front of the reflector and serving as a light source; and a front lens joined to and integrated with a front opening of the lamp body, the lamp unit for a vehicle being joined to a corner portion of the body of the vehicle, wherein the bulb is disposed horizontally with respect to the axis of the vehicle. Thus, the bulb insertion hole is omitted from the rear portion of the bulb so that the overall surface of the lamp body in the rear of the bulb is made to be the effective reflecting surface. As a result, the quantity of light which is emitted from the lamp can be enlarged.