To easily adjust an indication reference of a battery life. A CPU generates a maximum voltage value necessary for the operations of all functions of an electronic watch as a reference voltage of an analog quantity, inputs the voltage value to an A/D converting circuit to convert it into a digital value, stores the digital value outputted from the A/D converting circuit as a reference value corresponding to a voltage value necessary for each processing mode of the electronic watch into an EEPROM, converts the voltage value as an analog quantity of a battery into a digital value, and compares the digital value with the foregoing reference value to determine and indicate the battery life.