A touch screen device includes a circuit board, a power input port located on the circuit board, a main battery electronically connected to the power input port, and a stylus. A backup battery electronically connected to the power input port is located in the stylus. A power control unit is located on the circuit board. The power control unit detects the voltage value of the main battery, and compares the voltage value of the main battery with a predetermined voltage of the touch screen device. According to the comparative result, the power control unit switches between the main battery and the backup battery to provide power supply to the touch screen device.