The present invention discloses an antitheft apparatus mounted on a vehicle for protecting the vehicle from theft. The vehicle has a remote control device that controls a vehicle component of the vehicle in accordance with a control signal transmitted from a terminal. The antitheft apparatus includes an intruder detection part for detecting intrusion of an intruder, and an intrusion detection control part for controlling the detecting function of the intruder detection part during a period when the vehicle component is being controlled by the remote control device.