A fixing device for fixing an expansion card mounted with a cover plate, includes a frame and a fixing member. The frame includes a board defining an elongated slot, a plate extending in a substantially perpendicular manner from an end of the board and perpendicular to the slot, and a fixing portion extending in a substantially perpendicular manner from a side of the plate opposite to the board. A fastener is mounted to the frame adjacent to the slot of the board. The fixing member includes a sliding portion slidably mounted to the fixing portion and an operation portion extending in a substantially perpendicular manner from the sliding portion. The sliding portion defines an engaging hole to receive the fastener. The fastener is to be engaged with the cover plate. The fixing member is operable to sandwich the cover plate with the plate.