Battery voltage measuring circuit

A battery voltage measuring circuit is provided to decrease the manufacturing cost of a BMS(Battery Management System) by using a single CPU(Central Processing Unit) for controlling plural photomos relays. A battery controller for a hybrid vehicle or an electric vehicle includes a high voltage battery(40), a voltage measuring circuit(50), and an ADC(Analog Digital Converter)(60). The voltage measuring circuit independently utilizes the power of an insulated power supply(70) to measure a voltage of the high voltage battery. The power supply supplies a voltage from a differential amplifier to positive and negative terminals, when a photomos relay is connected in forward and reverse directions, respectively. The photomos relay is included in the voltage measuring circuit. The photomos relays are insulated from each other.