A portable electronic device in which microswitches (12) controlled by operation buttons (11) are mounted on one side of a printed circuit board (13), and circuit elements accommodated in BGA packages (14), (15) and (16) are soldered on the other side of the printed circuit board. In the portable electronic device, a shield wall (22) for surrounding the BGA packages (14), (15) and (16) is mounted on the printed circuit board (13), a first protrusion portion (18b) for holding down the shield wall (22) on the printed circuit board (13) is protruded from a case (18) of the portable electronic device (10), and second protrusion portion (18c) for holding down surfaces of the BGA packages (14); (15) and (16) on the printed circuit board (13) is protruded from the case (18) of the portable electronic device (10). With such a construction, the BGA packages are prevented from being peeled off from the printed circuit board (13). Further, even when the push buttons are frequently depressed in playing a game, the soldering parts of the BGA packages mounted on the back side of the operation button can be maintained in good conditions.