A stereo device testing method includes the following steps. Firstly, a stereo device is fixed, and a gas is continuously inputted into an inner space of the stereo device. After a predetermined time period, an internal pressure value of the inner space of the stereo device is detected. By judging whether the internal pressure value is higher than or equal to a default pressure value, the tester may determine whether the stereo device is qualified or not. After the stereo device is tested, the manufacturer of the stereo device may repair the gas leakage position. Since the influence of the gas leakage condition on the resonant effect is minimized, the sound quality of the stereo device is enhanced.