To provide a protecting device using a thermal fuse with a protecting circuit which widens an applicable area of the thermal fuse.

The protecting device 10 using the thermal fuse includes a load 14 connected with a power source and conveying a main current and a protecting circuit 20 for a thermal fuse 16 which has a predetermined operative temperature at which the same becomes operative when detecting an overheating of the load 14 and for a current sensor fuse 18 connected in parallel with the thermal fuse. The protecting circuit 20 including the thermal fuse 16 is connected in series with the power source 12 and the load 14 and as soon as the thermal fuse 16 becomes operative at a predetermined temperature, a conductive current flows into the current sensor fuse 18 and thereby electric discharge of the thermal fuse 16 is stopped.