A heat sink unit includes: a cooling member including a metal plate having a plurality of attachment holes on edges thereof, a first surface of the metal plate adjoining a heat-producing electronic component, and a second surface of the metal plate having a plurality of cooling fins erected on an area other than the attachment holes. The heat sink unit further includes: an attachment member including an opening in which the cooling fins are disposed when the cooling member is installed and a plurality of threaded bosses protruding from the first surface to be inserted into each of the attachment holes; and coil springs into which the bosses are respectively inserted. The coil springs are interposed between the attachment member and the metal plate, and the bosses are inserted into the attachment holes to fix the cooling member by screws.