A power cutoff device comprising: a relay unit including a switch which is configured to be in a connecting state in which the switch is electrically conductive and a cutoff state in which the switch is electrically non-conductive; a cutoff unit connected in series to the switch of the relay unit, the cutoff unit having a connecting state in which the cutoff unit is electrically conductive and an irreversible cutoff state in which the cutoff unit is electrically conductive irreversibly; a current detector configured to detect, in a first detection period, an object current flowing through the cutoff unit; and a controller configured to control the relay unit and the cutoff unit, characterized in that the controller is configured to: obtain a first changing rate of the object current with respect to time in the first detection period; cause the switch of the relay unit to be in the connecting state and cause the cutoff unit to be in the connecting state if determining that the first changing rate is not greater than a changing-rate threshold; and cause the relay unit to be in the cutoff state and cause the cutoff unit to be in the irreversible cutoff state if determining that the first changing rate is greater than the changing-rate threshold, wherein the controller is configured to previously store the changing-rate threshold, and the changing-rate threshold is determined based on a fluctuation rate of the object current when the object current is smaller than an overcurrent limit and fluctuates while power is supplied to a driving load. a relay unit including a switch which is configured to be in a connecting state in which the switch is electrically conductive and a cutoff state in which the switch is electrically non-conductive; a cutoff unit connected in series to the switch of the relay unit, the cutoff unit having a connecting state in which the cutoff unit is electrically conductive and an irreversible cutoff state in which the cutoff unit is electrically conductive irreversibly; a current detector configured to detect, in a first detection period, an object current flowing through the cutoff unit; and a controller configured to control the relay unit and the cutoff unit, characterized in that the controller is configured to: obtain a first changing rate of the object current with respect to time in the first detection period; cause the switch of the relay unit to be in the connecting state and cause the cutoff unit to be in the connecting state if determining that the first changing rate is not greater than a changing-rate threshold; and cause the relay unit to be in the cutoff state and cause the cutoff unit to be in the irreversible cutoff state if determining that the first changing rate is greater than the changing-rate threshold, wherein obtain a first changing rate of the object current with respect to time in the first detection period; cause the switch of the relay unit to be in the connecting state and cause the cutoff unit to be in the connecting state if determining that the first changing rate is not greater than a changing-rate threshold; and cause the relay unit to be in the cutoff state and cause the cutoff unit to be in the irreversible cutoff state if determining that the first changing rate is greater than the changing-rate threshold, wherein the controller is configured to previously store the changing-rate threshold, and the changing-rate threshold is determined based on a fluctuation rate of the object current when the object current is smaller than an overcurrent limit and fluctuates while power is supplied to a driving load.