A lamp having a fin provided in a periphery of a metal base. The fin includes a first surface close to a bright spot of a light-emitting tube and a second surface far from the bright spot on an opposite side of the first surface. A distance between a first inner edge of the first surface and a bright spot plane as a plane orthogonal to a center axis of the metal base including the bright spot is shorter than a distance between the bright spot plane and a first outer edge of the first surface. A distance between the first inner edge and the first outer edge of the first surface is not shorter than a distance between a second inner edge and a second outer edge of the second surface.