A protective circuit (1A) includes a protective element (10A), a plurality of secondary battery cells (20), (20), . . . , an external positive electrode terminal (30a) and an external negative electrode terminal (30b), an auxiliary power supply (40), a first control device (50), and a switch (60). The protective element (10A) has a first fusible conductor (15) of which both ends are connected to a first terminal (11) and a second terminal (12), and a heat generator (16) installed on a first energizing path (P1A) between a third terminal (13) and a fourth terminal (14). The auxiliary power supply (40) is provided electrically independently of the plurality of secondary battery cells (20), (20), . . . . In this protective circuit (1A), the switch (60) is switched to energization by a signal from the first control device (50), the heat generator (16) of the protective element (10A) generates heat, and the first fusible conductor (15) is fused to cut off a portion between the plurality of secondary battery cells (20), (20), . . . and the external negative electrode terminal (30b).