A device for retaining a printed circuit board is provided, which includes a first side plate and two second side plates. The first has at least one first rib perpendicularly protruding therefrom, each of the second side plate has at least one second rib perpendicularly protruding therefrom. The second ribs of the two second side plate are located in a same plane, and the plane that the second ribs of the two second side plates are located is spaced from that the first rib is located. When a printed circuit board (PCB) is placed in the device, the first rib presses against one side surface of the PCB, and the second rib press against the other side surface of the PCB, so that the PCB is retained in the device.