To prevent a wiper motor from being damaged by burning at the time of snow fall, to determine whether moter locking is adversely affected by snow, and to draw a clear line between single motor locking and a failure due to short-circuiting.

A wiper motor 2 drives a wiper in response to an operating signal from a wiper switch 11, a current detection part 41 detects current flowing to the wiper motor 2 from a power supply 1, and a shut-off control part 31 shuts off current to the wiper motor 2, when the value of current detected by the current detection part 41 exceeds a prescribed value. An ambient temperature sensor 13 detects ambient temperature, a lock judging part 33 determines whether or not the locking of the wiper motor is adversely affected by snow based on ambient temperature data from the ambient temperature sensor 13 and the presence of rain drops from a rain drop sensor 15 when current to the wiper motor 2 is shut off.