A fast hand-over method of a mobile device roaming in a wireless LAN environment includes: receiving GPS information; based on the received location information of the mobile device, searching one or more APs; by scanning the searched APs, detecting an AP to reassociate with; and reassociating with the detected AP. According to the method, when roaming in a wireless LAN environment, a mobile device calculates a moving path by using GPS information and then, by scanning only APs belonging to channels allocated to areas related to the moving direction, the mobile device can reduce a hand-over period, and as a result, a QoS guaranteed service can be provided continuously. Also, by using GPS information, the mobile device can selectively switch to an optimum network service in an area to which different network services are applied.