A monitoring system comprising: a monitoring section for acquiring information on a charge and discharge state of an electric storage device; and a determination section configured to determine whether the charge and discharge state of the electric storage device falls within an allowable range on the basis of the information acquired by the monitoring section, wherein the determination section has an output section configured to continuously output, to the monitoring section, a reference stepped signal made up of a High signal and a Low signal when the monitoring section is operating in a normal mode of acquiring information related to the charge and discharge state, and when the charge and discharge state of the electric storage device has been determined to fall within an allowable range, the determination section controls a period that the High signal and the Low signal of the reference stepped signal outputted to the monitoring section operating in the normal mode to be different from the period before the determination and outputs a diagnosis permit signal by changing the reference stepped signal so as to have a unique High signal and low signal for executing self-diagnosis to detect an abnormal event in the monitoring section, and the monitoring section is configured to determine whether a series of high signals and low signals received continuously from the determination section matches a unique pattern of high signals and low signals having the diagnosis permit signal, and when it has been determined to be matching, to stop the normal mode operation to execute a self-diagnosis for detecting an abnormal event in the monitoring section. a monitoring section for acquiring information on a charge and discharge state of an electric storage device; and a determination section configured to determine whether the charge and discharge state of the electric storage device falls within an allowable range on the basis of the information acquired by the monitoring section, wherein the determination section has an output section configured to continuously output, to the monitoring section, a reference stepped signal made up of a High signal and a Low signal when the monitoring section is operating in a normal mode of acquiring information related to the charge and discharge state, and when the charge and discharge state of the electric storage device has been determined to fall within an allowable range, the determination section controls a period that the High signal and the Low signal of the reference stepped signal outputted to the monitoring section operating in the normal mode to be different from the period before the determination and outputs a diagnosis permit signal by changing the reference stepped signal so as to have a unique High signal and low signal for executing self-diagnosis to detect an abnormal event in the monitoring section, and the monitoring section is configured to determine whether a series of high signals and low signals received continuously from the determination section matches a unique pattern of high signals and low signals having the diagnosis permit signal, and when it has been determined to be matching, to stop the normal mode operation to execute a self-diagnosis for detecting an abnormal event in the monitoring section.