A ground fault detection circuit includes: a first switch circuit that connects/disconnects a first path between a positive bus bar and a ground potential section, the positive bus bar being connected to positive electrodes of secondary battery units through a field-effect transistor including a parasitic diode; a second switch circuit that connects/disconnects a second path between a negative bus bar and a ground potential section, the negative bus bar being connected to negative electrodes of the secondary battery units; and a ground fault detection unit that detects a ground fault of the positive bus bar or the negative bus bar based on an electric current flowing through the first path or the second path.