A portable electronic device includes an antenna unit, a processor, a circuit board and a frequency switching circuit. The antenna unit includes a pin. The processor includes a signal control terminal to output a voltage control signal. The frequency switching circuit is disposed on the circuit board and connected to the signal control terminal and the pin, so as to switch the frequency of the antenna unit according to the voltage control signal. The frequency switching circuit includes a switch unit and an anti-noise unit. The switch unit is connected to the pin, and the anti-noise unit is connected to the signal control terminal and the switch unit.