The purchasing function directly affects the competitive ability of a firm. Purchasing managers need to periodically evaluate supplier performance in order to retain those suppliers who meet their requirements. An evaluation model is constructed in this study. Four attributes are selected to evaluate the vendor's performance: (1) quality, (2) delivery, (3) price and (4) service. An analytical hierarchy process (AHP) is employed to weight the criteria in an objective way. Then a technique for order preference by similarity to the ideal solution, TOPSIS, is applied to rank the alternatives for this evaluation. In order to demonstrate the workability of the model, an application example is also presented.