Electronic commerce has many advantages compared to the traditional way of doing business such as up to date information and rich service for less cost. There is a growing number of electronic commerce applications on the Internet. Using software agent technology, the market framework offers timesaving automation of auctions and flexibility through negotiations among the agents. In this research, we attempt to evaluate the performance of a negotiation decision function that considers the potential competitors in competitive market environment as well as that of a negotiation decision function that does not. For this evaluation, this study adopts the electronic marketplace as an application domain in which many sellers and buyers compete for limited resources in the marketplace.