The present disclosure is to provide a heatsink that can improve heat radiation performance of a heat radiating fin while preventing dry-out of a heat receiving portion and that can equalize a heat input in the heat receiving portion in an environment in which an installation space of the heatsink is limited even when a forbidden region exists in the installation space.
A heatsink including: a heat transport member having a heat receiving portion thermally connected to a heating element; and a heat radiating fin group which is connected to a heat radiating portion of the heat transport member and in which a plurality of heat radiating fins is arranged, wherein the heat transport member has an integral internal space that communicates from the heat receiving portion to the heat radiating portion and that is filled with a working fluid, a wick structure extended from the heat receiving portion to the heat radiating portion is housed in the internal space of the heat transport member, and the heat transport member has a heat radiating-side step portion, in which a step is provided in a direction that is not a direction parallel to a heat transport direction of the heat transport member, between a heat insulating portion placed between the heat receiving portion and the heat radiating portion and the heat radiating portion, the heat radiating portion being placed on a side of an installation surface of the heatsink compared to the heat insulating portion.