The projection lens of a lamp unit is configured as a toroidal lens. The toroidal lens extends in an arcuate profile having a central axis on a plumb line passing through a predetermined point on the optical axis behind the projection lens. Vertical cross sections of the arcuate profile have the same shape. The vertical cross section profile of the rear surface of the projection lens is configured by a rearward tilted straight line. The vertical cross section profile of the front surface of the projection lens is configured by a convex curved surface formed so as to position the rear focus point of the projection lens on the optical axis.