A battery pack includes a switching element, a heat resistor, and a fuse. The switching element turns to ON if the battery pack becomes in an abnormal state. The heat resistor is connected to the switching element and a battery in series. Current flows through the heat resistor when the switching element turns to ON. The fuse is located in a position where the fuse is heated by the heat resistor through which the current flows. The fuse is connected to the battery in series so that the fuse is disconnected with heat by the heat resistor at high temperature. Thus, the fuse cuts off a current flow in the battery. If the battery pack is in an abnormal state, when the capacity or voltage of the battery is less than a preset capacity or voltage value, the fuse is disconnected with heat by turning the switching element to ON.