A mounting apparatus includes a chassis, a mounting tray configured for being secured to an expansion card, and an expansion piece configured for securing the expansion card. The chassis includes a front plate. The mounting tray includes a front panel secured to the front plate, and a side panel connected to the front panel. A stopper piece is located on the front plate, and a clipping hole is defined on an end near to the front plate of the side plate. A flange and an inserting portion are positioned on opposite ends of the expansion piece, wherein the flange is secured to the stopper piece, and the inserting portion is inserted into the clipping hole.