To provide a method of selecting an optimal base station for each application when accumulating communication quality in response to an application type for a base station and a communication terminal switches base stations. A communication quality database 31 is prepared by assigning a current location of a communication terminal device, a currently running application program and a communication quality when executing an application program. When making a new connection with a base station, the current application and location is used to select a base station having an optimal communication quality from the communication quality database 31. This mechanism may be provided in the communication terminal device or may be provided as a communication system including a server device.