In-vehicle device, mobile terminal device, recognition support system, recognition support method, and recognition support program

An in-vehicle device performing communication with a mobile terminal device includes a vehicle exterior communication unit, an in-vehicle detection unit that detects a vehicle present location, a vehicle interior communication unit that acquires detection information on an object from a detection unit, and an in-vehicle control unit that generates recognition information including position information on the object based on vehicle position information indicating the vehicle present location and the detection information on the object and makes the vehicle exterior communication unit deliver the recognition information. The vehicle exterior communication unit receives existence notification information transmitted from the mobile terminal device when the mobile terminal device receiving the recognition information judges that the in-vehicle device has not recognized existence of a first object equipped with the mobile terminal device.