Provided are a battery state monitoring circuit capable of detecting disconnection of a battery from a power supply terminal or a ground terminal, and a battery device including the battery state monitoring circuit. The battery state monitoring circuit includes voltage detection circuits provided between the power supply terminal and an intermediate terminal and between the intermediate terminal and another intermediate terminal. For example, if a battery (21) is disconnected from a power supply terminal (11), the power supply terminal (11) is pulled down by a constant current circuit (15) to a voltage of a second intermediate terminal (13) so that a voltage detection circuit (34) detects the disconnection.