An assembled battery monitoring system includes: a voltage monitoring apparatus; discharging resistance elements and RC filters that are correspondingly coupled between battery cells of an assembled battery and the voltage monitoring apparatus; and discharging switches disposed in the voltage monitoring apparatus correspondingly to the battery cells. The voltage monitoring apparatus has at least three connection terminals for each of the battery cells. Two of the connection terminals are used to monitor a voltage of a corresponding battery cell through an output terminal of a corresponding RC filter, and at least one of a remainder of the connection terminals is used to form a discharging path of the corresponding battery cell when a corresponding discharging switch is turned on. Each discharging resistance element is disposed on the discharging path at a position that prohibits discharging of charges stored in a capacitor of the corresponding RC filter.