A drive device comprises a sensor for detecting a state of stress applied to a power transistor, a threshold voltage setting circuit for outputting a threshold voltage, an anomaly monitor circuit for determining whether or not a state of stress is abnormal by comparing a detected voltage of the sensor with the threshold voltage, and a control circuit for fixing the power transistor to either on or off when the state of stress is determined to be abnormal by the anomaly monitor circuit. When an operating mode is a test mode, the control circuit tests whether the anomaly monitor circuit determines the state of the stress is abnormal or not by switching a level of the threshold voltage set by the threshold voltage setting circuit so as to determine that a state of the stress applied to the power transistor is abnormal in the normally operating anomaly monitor circuit.