A keyless entry system includes an on-vehicle unit which is mounted in a vehicle, and a mobile device which is able to perform radio communication with the on-vehicle unit. The keyless entry system controls on-vehicle equipment mounted in the vehicle through radio communication between the on-vehicle unit and the mobile device. The on-vehicle unit has a plurality of LF transmission antennas (transmission antennas) for radio-transmitting a signal to the mobile device, and at least one of the plurality of LF transmission antennas is arranged in the vehicle interior of a door of the vehicle and is attached such that radiating magnetic flux passes through the window of the vehicle.