Abstract: A price revising system is devised to assist a purchaser to revise a trading contract on a commodity when the prices of materials, parts, etc. for a commodity changes due to changes in market conditions. The price revising system supports the trading contract by prompting the entry of the selling party data, the commodity, and a price fluctuation amount and then calculating a monetary effect with respect to an existing or future order of the commodity according to the fluctuation amount. The price revising system then allows the ordering party to check the monetary effect and communicate the monetary effect to the seller(s). The price revising system then creates a price revision to detailed price data according to the fluctuation amount for the commodity, presents a display prompting the selling party to approve the price revision, and executes the price revision in accordance with information indicating that the selling party has approved the price revision.