A wireless earphone device capable of providing balanced stereo. The wireless headset includes a Bluetooth earphone device, an audio adaptor, and a stereo earphone device for giving balanced sounds on both left and right channels. When the Bluetooth earphone device and the stereo earphone device are connected with the audio adaptor respectively, an audio switching module of the Bluetooth earphone device determines to transmit stereo audio signal with first channel signal and second channel signal to the stereo earphone device through the audio adaptor. Otherwise, only one channel of the stereo audio signal is transmitted from the audio switching module to a mono speaker unit on the Bluetooth earphone device.