A management server grants a reward to a provider of a video contributing to commodity's sales. The server determines whether a commodity introduction video conforms to a commodity introduction rule, registers the commodity introduction video, recommended store information in association with the commodity introduction video when a recommended store is introduced at a commodity purchase time, issues a viewing completion ID and registers the viewing completion ID in association with a user ID when viewing of the commodity introduction video by the user satisfies a predetermined condition, certifies that the user has purchased a commodity in the recommended store, and determines a reward to the video provider according to a predetermined reward determination rule when the purchase of the commodity in the recommended store by the user who has acquired the viewing completion ID is certified.