To urge an early bid of a commodity in a network auction.

A bid request for designating a bid price to a preregistered commodity is accepted via a network 2 (Step S1). Afterwards, when finishing a bid period, a bid request for designating the highest bid price is determined as a successful fixed bid up to finishing the bid period among the bid request (Step S2). A successful bid price is determined by gradually reducing the bid price in the successful fixed bid according to elapsed time up to finishing the bid period from acceptance of the successful fixed bid (Step S3).