A product retail sales management server for managing the retail sales of a product across a communication network comprises: a retail sales management module for managing the retail sales of the product; a price update module 13 for dynamically setting the price of the product in accordance with rules and the retail sales state of the product and in accordance with the actual retail sales state of the product when managed by the retail sales management module; and an acceptance module 11 for, upon the receipt of an information request via the communication network, furnishing a request transmission source with the information concerning the product and the price of the product, set by the price update module at the time the information request is received.