A communication system comprising a communication terminal and a management unit for managing connection setting information for connecting to a wireless communication network, wherein the communication terminal comprises: a connection setting information acquiring means for transmitting, to the management unit, an "un-connectable" message indicating that a wireless communication network associated with the connection setting information registered in the communication terminal cannot be connected, and for acquiring, from the management unit, the connection setting information of a wireless communication network currently available by the communication terminal; • a connection setting registering means for registering the connection setting information acquired by the connection setting information acquiring means; and • a connection executing means (13, 14) for connecting to a wireless communication network associated with the connection setting information registered by the connection setting registering means, and the management unit comprises: • a location information acquiring means for acquiring location information of the communication terminal from a communication network which manages location information of the communication terminal, based on a telephone number called from the communication terminal which sent the "un-connectable" message, if the "un-connectable" message is received from the communication terminal; • a connection setting information extracting means for extracting, from the connection setting information of the wireless communication network preliminarily stored, the connection setting information of a wireless communication network currently available by the communication terminal, based on the called telephone number and the acquired location information; and • a connection setting information transmitting means for transmitting the extracted connection setting information to the communication terminal. a connection setting information acquiring means for transmitting, to the management unit, an "un-connectable" message indicating that a wireless communication network associated with the connection setting information registered in the communication terminal cannot be connected, and for acquiring, from the management unit, the connection setting information of a wireless communication network currently available by the communication terminal; • a connection setting registering means for registering the connection setting information acquired by the connection setting information acquiring means; and • a connection executing means (13, 14) for connecting to a wireless communication network associated with the connection setting information registered by the connection setting registering means, and • a connection setting registering means for registering the connection setting information acquired by the connection setting information acquiring means; and • a connection executing means (13, 14) for connecting to a wireless communication network associated with the connection setting information registered by the connection setting registering means, and the management unit comprises: • a location information acquiring means for acquiring location information of the communication terminal from a communication network which manages location information of the communication terminal, based on a telephone number called from the communication terminal which sent the "un-connectable" message, if the "un-connectable" message is received from the communication terminal; • a connection setting information extracting means for extracting, from the connection setting information of the wireless communication network preliminarily stored, the connection setting information of a wireless communication network currently available by the communication terminal, based on the called telephone number and the acquired location information; and • a connection setting information transmitting means for transmitting the extracted connection setting information to the communication terminal. • a location information acquiring means for acquiring location information of the communication terminal from a communication network which manages location information of the communication terminal, based on a telephone number called from the communication terminal which sent the "un-connectable" message, if the "un-connectable" message is received from the communication terminal; • a connection setting information extracting means for extracting, from the connection setting information of the wireless communication network preliminarily stored, the connection setting information of a wireless communication network currently available by the communication terminal, based on the called telephone number and the acquired location information; and • a connection setting information transmitting means for transmitting the extracted connection setting information to the communication terminal.