A wiper device is provided with a wiper arm including an arm head, a retainer and a coil spring, and with a lock-back detecting device which detects whether or not the wiper arm is in a "lock-back" state and shuts off a power supply to the motor in case of detecting the wiper arm to be in the "lock-back" state. This device makes it possible to prevent a vehicle hood from being hit by the wiper arm or the wiper blade.