An expansion card fastening device includes a bracket, a first fastener, and a second fastener. The bracket includes parallel arranged fences. The first fastener is assembled on one of the fences, and includes a connecting portion, a supporting portion, and an elastic element. The supporting portion and the elastic element are both disposed on an end of the connection portion. A first clasp protrudes from the supporting portion, and faces the same direction with a free end of the elastic element. A second fastener pivots to the supporting portion, and is resisted by the elastic element. A second clasp protrudes from the second fastener, and faces the same direction with the first clasp.