A voltage monitoring system includes a plurality of voltage monitoring devices connected to each other in series for monitoring a voltage of each of battery units obtained by dividing per specific number a plurality of batteries connected in series. Each of the voltage monitoring devices includes a reception unit for receiving specific information transmitted from a former stage; a storage unit for storing the specific information received with the reception unit as self specific information; and a transmission unit for adding predetermined information to the specific information received with the reception unit, and for transmitting the specific information to a later stage as later stage specific information.