A charge-discharge device and a control method of the charge-discharge device are provided. The control method of the charge-discharge device comprising: receiving an input voltage signal via a configuration channel of a USB port; sampling the input voltage signal in a predetermined period to generate a plurality of sampling values; selectively connecting the configuration channel to a pull-down circuit or a pull-up circuit according to the sampling values, receiving a first charging voltage via a power channel of the USB port when the configuration channel is connected to the pull-down circuit, and outputting a second charging voltage via the power channel when the configuration channel is connected to the pull-up circuit.