Universal serial bus apparatus with variable voltage

The present application discloses a universal serial bus (USB) apparatus with variable voltage which utilizes a digital-to-analog converter (DAC) coupled with a divider resistor to serve as a dual role port under type-C communication protocol of universal serial bus, where the DAC is regarded as a voltage signal generation unit for generating the variable voltage. When the USB apparatus is identified as a discharge apparatus, the voltage signal generation unit generates a particular non-zero partial voltage at a configuration channel pin electrically connected to an exterior apparatus, and thereby the exterior apparatus confirms the discharge capacity of the USB apparatus. When the USB apparatus is identified as a charged apparatus, the configuration channel pin gained a partial voltage from the exterior apparatus and the divider resistor is grounded. The present application reduces an amount of necessary elements and volume of the apparatus and preserves reasonable configuration for power supply.