Each fin of a heat sink includes a main fin connected to a core and extending radially outwards, and a pair of branch fins extending radially outwards from a branch point at a radially outer end of the main fin. Among a plurality of fins, in each of three fins which are adjacent in the circumferential direction, a width of an end portion of the main fin viewed along the center axis expands radially outwards at an angle which is larger than an expanding angle of the pair of branch fins. A difference between a distance from the center axis to the branch point in the center one of the fins and a distance from the center axis to the branch point in each of the other two fins is equal to or larger than a width of a root of the main fin in the center radiating fin.