To provide a failure detection system of a DC motor for detecting the existence of disconnection failure without rotating the DC motor.

The DC motor 5 is driven by an H-bridge circuit composed of switching elements 1-4. The H-bridge circuit receives direct current power from a high potential power source Vh and a low potential power source Vl. Internal resistors of a minute current detection circuits 6 and 7 have high values of several kΩs and are connected between both the power source terminals of the DC motor and the low potential power source Vl. If disconnection exists between both the power source terminals of the DC motor, the switching element 1 is turned on, minute current is made to flow at voltage (Vh-Vl) in the circuit 6 by turning off the other switching elements, and a signal 105 is at an LO level. Since the current does not flow in the circuit 7, the disconnection of the DC motor is detected with a detection circuit 8 since a signal 106 is at an HI level.

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