To provide a diagnostic system for insurance enabling a customer to voluntarily have the contents of the contracts of an insurance diagnosed objectively.

Insurance policy patterns of formats unique to each of insurance companies 4a to 4n are stored in the insurance company information database 3a of a diagnostic site 3A. When a customer inputs the name of an insurance company and a policy number to the basic information input screen of a terminal 1a, the diagnostic site 3A obtains the insurance policy pattern corresponding to the policy number of the corresponding insurance company from the database 3a and transmits it to the terminal 1a. When the contracts of the insurance policy are input as viewed to a contract input screen displayed on the terminal 1a, they are stored in a customer contract database 3b. The diagnostic site 3A downloads from the database 3b the contracts of the insurance for which the customer has desired diagnosis, and diagnosis on the insurance is performed in an interactive mode, with the results being displayed on the terminal 1a and stored into a diagnostic result database 3c.