Theft detection mechanism and anti-theft device for vehicle

摘要

A theft detection mechanism is provided with a top ring 28 which is sunk when a foreign substance D other than a key K is inserted into a key inserting hole 32c and a sinking sensor for detecting that the top ring is sunken. A top ring is inevitably pushed down when a foreign substance other than a key is inserted into a key inserting hole to activate a sinking sensor, thereby detecting thieving action with reliability. Moreover, a structure of a theft detect ion mechanism is made simple to reduce the cost thereof.