GATEWAY SYSTEM

PROBLEM TO BE SOLVED: To solve the problem that large-scale modification is required to be performed or update of a system is required to be performed to realize connection between the conventional information system and an open network since the conventional information system is not developed on the assumption of the connection with the open network. SOLUTION: A gateway site 10 nudges whether or not combination between a transmitting origin and a receiving destination added to data is right by referring to combination information 150 of transmitting/receiving destinations after covering communication procedures when the data is received from a customer site 30. Data decoding, conversion of character code, data code and data form, data encoding, conversion of the communication procedures to conform to the combination between the transmitting and receiving destinations are performed while referring to tables in which the respective pieces of information are stored afterward. After that, the data are transmitted to a customer site 40.