To provide a movable body theft prevention system with an improved theft prevention effect by making it difficult to bypass a theft prevention function and start a power source of a movable body.

The theft prevention system comprises a theft prevention device 2 for preventing a vehicle from being stolen, an engine ECU 3 for controlling an engine 4 of the vehicle, and an on-vehicle LAN 9 for connecting the theft prevention device 2 and the engine ECU 3 so as to execute data communication. The theft prevention device 2 comprises a fingerprint sensor 21 for authenticating fingerprints, a characteristic extracting part 22 for extracting characteristic data of the fingerprints, and a communication control part 28 for sending the extracted characteristic data as discrimination data to the engine ECU 3. The engine ECU 3 comprises a communication control part 31 for receiving the discrimination data, a matching part 36 for matching the discrimination data to discrimination source data, and an engine control part 39 for allowing the engine 4 to start on condition that the discrimination data correspond to the discrimination source data.