To provide a crime preventive system having an alarm device capable of precisely grasping a locking-unlocking state of a locking-unlocking device, even when trying fraudulent unlocking using a magnet from an external part; and an opening part device having the crime preventive system.

This crime preventive alarm device is applied to the locking-unlocking device 100 having a rotary part 103 and a fixed part 101. The device has the magnet 120 built in the tip vicinity of the rotary part, a first magnetic sensor 125 built in the fixed part, and arranged in a position corresponding to the magnet in locking, a second magnetic sensor 127 arranged in a magnet unsensible position in an operation range of the rotary part in the vicinity of the first magnetic sensor, and a control part 150 for receiving a sensing signal of the first and second magnetic sensors. The control part transmits a signal of the effect of causing the abnormal situation, when both the first and second magnetic sensors do not issue the sensing signal, and when the second magnetic sensor issues the sensing signal.