The present invention is to provide a voltage detecting apparatus, which can downsize a circuit, reduce costs and detect a voltage with high accuracy, the voltage detecting apparatus to detect a voltage by using a flying capacitor. Furthermore, the voltage detecting apparatus does not halt whole functions. The first zener diode is connected to the first resistor R1, which divides a voltage stored with the capacitor as a flying capacitor into a detectable voltage at a microcomputer, in parallel. Furthermore, the voltage detecting apparatus prevents more than a zener voltage of the first zener diode from applying to the input of the microcomputer.