To provide an intrusion preventing device capable of storing an intrusion preventing body in the device, miniaturizing the whole device, and prolonging the interval between the device and the suspended side of the intrusion preventing body.

A link chain 2 serving as an intrusion preventing body is sent into a case body 4 by a feeding means 8 and is dropped and stored in a storage section 9 provided on the lower side of the feeding means 8. Since the storage section 9 can store the link chain 2 by the capacity of the storage section 9, the whole length of the link chain Z can be prolonged, and the interval between an intrusion preventing device 1 and the suspended side of the link chain 2 (intrusion preventing body) can be prolonged. The link chain 2 is not wound on the feeding means 8, the feeding means 8 can be miniaturized, and the whole intrusion preventing device 1 can be miniaturized.