To inquire customer information by specifying a customer without changing an account number or the like even when a plurality of financial institutions use one information server 10.

A multi-bank customer information inquiry system is characterized in that an information server 10 comprises: a customer information preservation section 15 (15a-15n) for storing a financial institution code 31 and the customer information for each financial institution ; an inquiry right judgment information preservation section 16 for storing the financial institution code 31 of an inquiry-approved financial institution terminal 20 (20a-20n); an inquiry right judgment section 12 for judging the inquiry right of the financial institution terminal 20 from the inquiry right judgment information preservation section 16 on the basis of the inquiry-requesting financial institution code 31 when an inquiry request arises from the financial institution terminal 20; and a retrieval section 13 for retrieving the customer information from the customer information preservation section 15 of the financial institution on the basis of the financial institution code 31 when the inquiry right is confirmed and outputting the customer information.