To make effectively issuable an alarm when a part of a window glass is broken and a lock mechanism is illegally opened and to prevent an alarm function from being damaged even when performing erroneous operation.
A detection means 3 is assembled in a key main body 2 of the window glass to issue alarm sound by an alarm means based on the detection of the detection means 3, and an alarm release button 21 for releasing the occurrence of the alarm sound is provided. When the alarm release button 21 is pressed while an operation knob 7 is at a locking position, an alarm is not issued even if the operation knob 7 is set to a lock opening position. When the operation knob 7 is operated and an alarm is issued, the alarm sound is not stopped by merely returning the operation knob 7 to the locking position, and the alarm sound is not stopped unless the alarm release button 21 is simultaneously pressed.