A heat sink includes: a base plate; and at least one fin secured to the base plate; wherein the base plate has at least one through hole that extends in a first direction parallel to a surface of the base plate, wherein the at least one fin has a projection inserted into the at least one through hole, and wherein, in a second direction that is parallel to the surface of the base plate and that is perpendicular to the first direction, both end surfaces of the projection are in contact with inner wall surfaces of the at least one through hole entirely in a third direction parallel to a thickness direction of the base plate.