To prevent not only wasting of resources, but also unnecessary radio wave interference in peripheral areas of a vehicle in the middle of a travel resulting from transmission of a radio wave from the vehicle during the travel when antennas for wireless LAN access point is installed inside and outside the vehicle.

The on-board wireless LAN system which has a wireless LAN access point, an Internet connection means, and the wireless LAN antennas and is mounted on the vehicle has a vehicle state detecting means of detecting the current state of the vehicle, a vehicle state discrimination means of discriminating the state of the vehicle based upon the detection results thereof, a control signal generating means of generating a signal for controlling the operation of the wireless LAN antenna outside the vehicle based upon the discrimination results, and an antenna control means of controlling the output of the wireless LAN antenna outside the vehicle based upon the generated control signal, thereby transmitting no unnecessary radio wave to outside the vehicle during a travel and providing services of wireless LAN inside and outside the vehicle during a stop.