A power-supplying device comprising: a terminal (120, 121) configured to be connected to an external device; a rechargeable battery configured to output electrical power to the external device via the terminal; a first shutdown circuit (105, 107) positioned at a plus side of the rechargeable battery, the first shutdown circuit being configured to interrupt electricity over a first path (131, 133) between the rechargeable battery and the plus side of the terminal; a second shutdown circuit (109A, 109B) positioned at a minus side of the rechargeable battery, the second shutdown circuit being configured to interrupt electricity over a second path between the rechargeable battery and the minus side of the terminal; and a controller configured to control the first shutdown circuit and the second shutdown circuit, characterized in that: the power-supplying device further comprising: a step-down circuit configured to apply a prescribed voltage to the controller, the step-down circuit configured to be connected to an external charger through a third path; and a switching circuit, the step-down circuit is further configured to be connected to the rechargeable battery via the switching circuit, the controller is configured to control the switching circuit to turn on and off electrical connection between the rechargeable battery and the step-down circuit. a terminal (120, 121) configured to be connected to an external device; a rechargeable battery configured to output electrical power to the external device via the terminal; a first shutdown circuit (105, 107) positioned at a plus side of the rechargeable battery, the first shutdown circuit being configured to interrupt electricity over a first path (131, 133) between the rechargeable battery and the plus side of the terminal; a second shutdown circuit (109A, 109B) positioned at a minus side of the rechargeable battery, the second shutdown circuit being configured to interrupt electricity over a second path between the rechargeable battery and the minus side of the terminal; and a controller configured to control the first shutdown circuit and the second shutdown circuit, characterized in that: the power-supplying device further comprising: a step-down circuit configured to apply a prescribed voltage to the controller, the step-down circuit configured to be connected to an external charger through a third path; and a switching circuit, the step-down circuit is further configured to be connected to the rechargeable battery via the switching circuit, the controller is configured to control the switching circuit to turn on and off electrical connection between the rechargeable battery and the step-down circuit. the power-supplying device further comprising: a step-down circuit configured to apply a prescribed voltage to the controller, the step-down circuit configured to be connected to an external charger through a third path; and a switching circuit, a step-down circuit configured to apply a prescribed voltage to the controller, the step-down circuit configured to be connected to an external charger through a third path; and a switching circuit, the step-down circuit is further configured to be connected to the rechargeable battery via the switching circuit, the controller is configured to control the switching circuit to turn on and off electrical connection between the rechargeable battery and the step-down circuit.