PURPOSE: To use a home banking service system through a PBX extension subscriber terminal by storing allocation information as subscriber information.

CONSTITUTION: In this system, relation between the number (n) of extension subscriber terminals 6 and the number (m) of public telephone lines which connect a PBX(private branch exchange) 10 to a public network 1 is shown ordinarily in n>m. In such a case, some of public telephone lines connected from the PBX 10 to the public network 1 are registered in advance as the one for home banking service. This system is made in such a way that the PBX extension subscriber terminal 6 registered as the one for home banking service and a specific public telephone line are allocated. In other words, an allocation information storage means 11 which stores the allocation information as the subscriber information stores a specific number required for the analysis of the home banking service, the network ID of a home banking service subscriber, a password to hold security and the correspondence relation of the network ID and an output trunk in accordance with the PBX 10, etc.