This paper considers a web-based order processing system under SCM environment. Following the framework of B2B electronic commerce, we focus on activities closely related to order handling within the supply chain. We also try to integrate the order processing system with the overall information system of the company. The methodology is applied to the case of H company and a prototype system is designed. This study analyzes the current product estimate and order handling process in the point of view of both the purchasing and the selling companies. It intends improvement by changing the existing closed way of request and offering estimate through fax or VAN into an open way using internet. For this, a company should be registered on the order site of internet. Then it can request estimate, take estimate, and handle order through internet adopting the concept of electrical commercial transaction.