The present invention discloses a USB application device including a body, a circuit board, a pins plate and a plurality of first electrical pins. The plurality of first electrical pins are enclosed previously by the pins plate, and a first end of each one of the plurality of first electrical pins is connected on the circuit board, so that the plurality of first electrical pins pass over a first surface of the circuit board and thus extend in suspension. The circuit board is disposed within the body and the pins plate is combined with the body, so that the plurality of first electrical pins are partly exposed by the body. The present invention also discloses a method for assembling a USB application device, which is capable of simplifying the process of disposing the plurality of first electrical pins on the circuit board.