This study investigates the performance of firms that supply to large companies. When supplier firms are trading with a big firm that has strong bargaining power, suppliers’ bargaining power is weakened. We assume that the difference in the bargaining powers will have an effect on the performances of supplier firms and this paper also analyzes the difference in the performances of supplier firms with big-buyer firm and nonsupplier firms. If the big firm is making profits by imputing costs on supplying firms, then the difference in performances between the big firm and suppliers’ has to show a negative relationship. But from the analysis, we can see that big firm’s performance is having a positive relationship with the performance of suppliers. Also, we anticipated a better performance of non-supplier firms compare to supplier firms because of reasons such as lowering delivery prices. The result shows, however, except for gross margin, operating margin, return on sales(ROS), return on asset(ROA) and return on equity(ROE) had no differences, and in a few, supplier firms had better performance than non-supplier firms. We found out that even though supplier firms had lower gross margin compare to non-supplier firms, ROA and ROE were higher because of the asset utilization. Supplier firms had higher asset turnover, account receivable turnover and inventory turnover, than non-supplier firms, which tells us that assets were managed more efficiently in supplier firm. Therefore, cash conversion cycle, which is a measurement used to obtain days’ account receivables, days’ account payables and days’ inventory, is shorter which states that from the day of buying raw materials to the day of collecting expenses is done swiftly. These results held after controlling endogeneity.