PROBLEM TO BE SOLVED : To refer to a plurality of pieces of customer attribute information related to a specific contract, in a customer dealing system of a provider providing prescribed service. SOLUTION : Contract-related information 51 is information wherein index information of customer information related to a prescribed contract number is associated to the contract number. In the contract-related information 51, the contract number 511 is associated to a landowner number 512. Next, the contract number 511 is associated to a neighborhood association-neighborhood self-governing body number 513, and the neighborhood association-neighborhood self-governing body number 513 is associated to a neighborhood association-neighborhood self-governing body officer number 514. The contract number 511 is associated to an apartment house resident number 515, the apartment house resident number 515 is associated to an apartment house number 516, and the apartment house number 516 is associated to a house owner number 517 and a real estate number 518. Thereby, because the index information of each information related to the designated contract number 511 can be specified, each information can be promptly acquired from each DB (database). COPYRIGHT : (C)2009, JPO&INPIT