An abnormal-voltage protection apparatus includes a switch unit, a voltage detection unit, and a delay time control unit. The switch unit is coupled to a power supplying path formed between an AC power source and a load. The voltage detection unit detects the AC power source and provides a detection signal. The delay time control unit is coupled to the voltage detection unit and the switch unit, and receives the detection signal and provides a control signal to the switch unit according to the detection signal. When the voltage detection unit detects that the AC power source changes from an abnormal voltage to a normal voltage, the delay time control unit turns on the switch unit by the control signal after a delay time so that the AC power source supplies power to the load through the power supplying path.