A once-through forced air-cooled heat sink according to the present invention comprises: a heat sink portion which is configured to be attached to an object that is to be cooled; and a blower for introducing cooling air into the heat sink portion. The heat sink portion comprises: an air inlet; an air outlet; and fins for dissipating heat in the object with the aid of cooling air which is supplied by the blower. The air inlet, the air outlet, and the fins are arranged such that the cooling air is introduced from the air inlet, then cools the fins and flows to the air outlet in a once-through pattern.