A lamp unit used in a vehicular lamp includes a reflector provided with a parabolic cylindrical reflective surface with a focal line in the horizontal direction; a planar light source having a light-emitting surface with a generally oblong shaped region; and a drive portion that rotatably supports the semiconductor light-emitting element portion. The generally oblong shaped region of the planar light source includes a long side in a direction parallel to the focal line and a short side of a predetermined width. The planar light source is disposed such that the light-emitting surface faces the parabolic cylindrical reflective surface of the reflector and such that a long side, on a lamp front side, generally coincides with the focal line and acts as a rotational axis.