A fastening structure for an expansion card is provided. The card has a baffle and one end of the baffle is formed with a bending portion and a first long hole. The fastening structure includes a flat plate located at one side of a case and has a plane extending toward inside the case; a first supporting portion and a second supporting portion fastened at the plane of the flat plate; a fastening member having a pressing portion and at least one second long hole. The fastening member is disposed at the first supporting portion via the second long hole, and slidably leans against the plane. The pressing portion extends toward the bending portion. When the fastening member slides to a fixing position, the pressing portion presses the bending portion, and the baffle is fastened at the second supporting portion via the first long hole and leans against the plane.