A state monitoring unit monitors a state of an assembled battery in which a plurality of unit cells are connected in series. The state monitoring unit includes: a plurality of voltage monitoring devices provided in a high voltage side and a controller provided in a low voltage side electrically isolated with the high voltage side. The controller transmits a common voltage measurement command to the respective voltage monitoring devices connected via a communication channel in a daisy-chain scheme. The controller includes a storage for storing latency time determined based on a required time for each of the voltage monitoring devices elapsing from transmission of the common voltage measurement command with respect to the communication channel to voltage measurement of the unit cells, and measures charging/discharging current of the assembled battery when the latency time has elapsed from the transmission of the common voltage measurement command with respect to the communication channel.