To provide a secondary battery protector which can satisfy fundamental functions, such as protection against overcharging and overcurrent of a secondary battery, and can achieve simplification of circuits, cost reduction and size reduction.

The secondary battery protector is constituted of a switching circuit 14, which is connected in parallel to a charging circuit 2 supplying electric power to a secondary battery 1 and is energized by a voltage higher than the threshold voltage, a heating element 12 connected in series with the switching circuit 14, and a thermally actuated element 10, having a structure which switches the supply of electric power by means of the heating itself by the supply of power or the heat from the heating element 12 from the secondary battery 1, to the heating element 12.