To reliably prevent any error alarm of a vehicle theft prevention device while transporting a vehicle.

The vehicle theft prevention device comprises a theft detection means for detecting the theft of a vehicle, an alarm means for giving alarm when detecting the theft of the vehicle by the theft detection means, and a transport determination means for determining whether or not the vehicle is in a transporting mode. The vehicle theft preventive device is transited to a transport mode for prohibiting the alarm by the alarm means when the transport determination means determines that the vehicle is under transport, and to a normal mode for permitting the alarming by the alarm means when the transport determination means determines that the vehicle is not under transport.