A circuit board device includes a secondary circuit board supported on a primary circuit board and parallel to the primary circuit board for forming a compact structure. The secondary circuit board includes one end coupler for coupling to another coupler of the primary circuit board, and the other end having one or more rods supported on a frame for allowing the secondary circuit board to be stably supported on the primary circuit board. A housing may prevent the secondary circuit board from being interfered by the electromagnetic field of the primary circuit board.