Heat-dissipating device for expansion card and expansion card assembly with heat-dissipating function

A heat-dissipating device for expansion card is used to dissipate redundant heat of an expansion card. The expansion card has a printed circuit card, an inserting-type connecter formed at one end of the printed circuit card and a screwing hole formed at the other end of the printed circuit card. The heat-dissipating device includes a base plate, a plurality of fins, a screwing portion and at least one hooking part. The base plate has a flat bottom surface, a first side and a second side opposite to the first side. The fins are upward protruded from a top surface of the base plate. The screwing portion is formed at the first side of the base plate. The position of the screwing portion is corresponding to that of the screwing hole of the expansion card. The at least one hooking part is disposed at the second side of the base plate and is hooked with one side of the printed circuit card of the expansion card.