To realize a battery state monitoring circuit in which detection is reliably made even if a continuous noise is entered, and to provide a battery device which has a long life and is safe. In the battery state monitoring circuit, the detecting circuit outputs a signal for controlling a switch circuit in accordance with a state of the secondary battery with respect to one of a specified voltage value and a specified current value. The signal includes one of: a detection signal for starting one of charge protection and discharge protection of the secondary battery; and a release signal for releasing the one of the charge protection and the discharge protection of the secondary battery. A switching rate from the release signal to the detection signal is higher than a switching rate from the detection signal to the release signal.