An ECU (vehicle-mounted device) is provided with a fuse F1 and a blow sensing circuit. The blow sensing circuit monitors a fuse voltage between two connection nodes respectively positioned on the upstream and downstream sides of a fuse in a current path of a current flowing through the fuse from the positive pole of a DC power supply. The blow sensing circuit, if the fuse voltage is lower than a voltage threshold value, outputs a voltage lower than a reference voltage. The blow sensing circuit, if the fuse voltage is greater than or equal to the voltage threshold value, outputs a voltage greater than or equal to the reference voltage.