A battery monitoring system includes a battery monitoring ECU and battery monitoring devices which are sequentially connected in a connection configuration. The battery monitoring ECU includes a clock generator that generates a first clock signal. Each battery monitoring device includes a second clock generator that generates a second clock signal, a controller that causes a frequency correction block to correct a frequency of the second clock signal in line with the first clock signal and causes the battery monitor to monitor a battery cell using the second clock signal that has been corrected, and a switch that, according to an instruction of the battery monitoring ECU, switches a circuit configuration to a state in which a signal received from a preceding device is transmitted to a succeeding device in the connection configuration.