To provide a DC motor controller in which a DC motor is prevented from being stopped erroneously in operation due to erroneous judgment of locked state.

The DC motor controller comprises a relay 31 for turning power supply to a DC motor 3 on/off, a power ground line 30 connected with the DC motor 3 and a rear defogger 4, a comparator 2 for judging the current of the DC motor 3, and a microcomputer 1 for turning the relay 31 off based on the output signal therefrom. Output signal from the comparator 2 goes low when the DC motor 3 is locked and since a microcomputer 1 is low active, it does not make an erroneous judgment of locked state even if a high current flows through the rear defogger 4 and the power ground line 30 is floated from the ground. Consequently, the DC motor 3 is prevented from being stopped erroneously in the way of operation.