PURPOSE: To obtain an abnormality detection apparatus which prevents the breakdown of a peripheral apparatus due to an overcurrent by a method wherein, when a state that the deviation of a current detection value with reference to a current instruction value is larger than a prescribed threshold value is continued for a definite period or longer, a current output system to a motor is judged to be abnormal and a power supply to the motor is stopped.

CONSTITUTION: In an abnormality judgment part 2c, the deviation of a current detection value with reference to a current instruction value supplied from a current comparison part in a continuity state that a relay 3 has been turned on is compared with a threshold value, for abnormality detection, which has been stored in a judgment-value storage part 2d. Then, when the deviation is larger than the threshold value while a definite period which is clocked by a timer 2e elapses, the abnormality judgment part 2c regards an abnormality as have been occurred in the output system of a motor M, it outputs a power- supply-stop instruction to a current-instruction computation part 2f, and it outputs an OFF-instruction to the relay 3 so as to stop a power supply to the motor M. Thereby, it is possible to prevent the breakdown of a peripheral apparatus due to an overcurrent.