When collision detection unit such as a G sensor or a radar sensor detects a collision of a two-wheeled vehicle with a car body, a protection determination unit determines the necessity for protection. When it is determined that protection is required, at least one protection net are unfolded in response to the strength of the collision, etc. If the human body of the driver, passenger, etc., of the two-wheeled vehicle attempts to jump the car body in the collision, the human body can be caught in the protection net for making it possible to prevent a secondary disaster from occurring.