A riser card module includes a frame body, a carrier plate connected to the frame body for abutment against first surfaces of positioning plates of fixing brackets of expansion cards, a riser card disposed on the frame body and having a plurality of expansion slots for insertion therein of the expansion cards, respectively, and a limiting unit rotatable relative to the carrier plate about an axial direction which is perpendicular to a longitudinal direction of the carrier plate for abutment against second surfaces of the positioning plates of the fixing brackets of the expansion cards so as to restrict movement of the expansion cards relative to the riser card.