Technology for realizing reductions in time required for production plan by estimating supply capacities of suppliers is provided. A system has a function of registering and displaying transaction information including delivery requests from a buyer including number of required parts and delivery responses from a supplier including number of suppliable parts, a function of managing the series of transaction information as transaction history information on a DB, and an estimating function of estimating supply capacities of parts of the supplier with respect to the delivery responses in reply to delivery requests. The estimating function performs processes of estimating supply capacities by determining numbers of suppliable parts of past delivery responses with respect to numbers of required parts of past delivery requests by using the delivery request history information, the delivery response history information and the process LT information, and outputting a screen including the estimated result information to users.