A battery management system includes a monitoring device and a control device. The control device transmits request data requesting transmission of battery information, and the monitoring device transmits response data including the battery information to the control device. The control device makes next request data include communication establishment information and transmits the next request data. The monitoring device includes a transmission buffer capable of individually accumulating the battery information for multiple times. The monitoring device deletes the battery information corresponding to communication establishment from the transmission buffer, and holds the battery information corresponding to communication failure in the transmission buffer based on the communication establishment information.