A USB application device includes a casing, a printed circuit board and a flexible supporter. The casing has a receiving space therein. The printed circuit board is completely receiving the printed circuit board and includes a top surface and a bottom surface opposite to the top surface. A plurality of contacts is disposed on the top surface of the printed circuit board. The flexible supporter is arranged in the casing and between the casing and the bottom surface of the printed circuit board. If the USB application device couples with a mating connector, the mating connector press the printed circuit board to urge the printed circuit board to press the flexible supporter. The flexible supporter is urged to be deformed by the press of the printed circuit board and to disperse the pressing force from the mating connector.