To obtain a crime preventing system lock for detecting insertion of a tool like a ripping bar to prevent illegal unlocking and damage to a guard plate by breakage of a door frame or a door, and to deter a loss caused by unlocking by breakage.

The crime preventing system lock 100 is mounted across the door frame 11 and the door 15. The door 15 is openably/closeably mounted on the door frame 11 and is brought into a state of locking by allowing a deadbolt protruding from a butt end to proceed into a strike box formed in the door frame 11. The system lock 100 comprises a microswitch mounted on the strike box to detect a locking state by being operated by the entering of the dead bolt, a tape switch provided in a gap between the door frame 11 and the door 15 to detect a change in pressure, and an alarm sound emitting part. The system lock 100 is provided with an alarming circuit for supplying electricity for alarming from a power source to the alarm sound emitting part by a locking detecting signal from the microswitch and a pressure change detecting signal from the tape switch.