In this study, we analyzed the financial efficiency of 33 domestic automobile parts manufacturing companies using directional distance function including harmful output. In addition, a new ratio indicator based on the efficiency measurement method is presented by presenting the optimum financial efficiency ratio within the group. As a result of the efficiency analysis, the average financial efficiency of 33 automobile body parts manufacturing companies is about 89.55% and the standard deviation is about 12.07%, which is considered to have good overall financial efficiency. However, it is judged that there is a difference in the degree of financial efficiency between companies is significant. In addition, a total of 15 companies showed efficiency scores of less than 90%, suggesting that about 45% of companies need to improve their financial efficiency. In the analysis of the financial efficiency ratio, which is a ratio of the target value to the improvement target of inputs and output variables, the total of 13 companies with financial efficiency shows a very good index in terms of operating profitability and asset profitability. Relatively, the debt-to-equity ratio of the financial stability index is slightly higher than the overall average. It is expected that the ratio of relative financial efficiency in the group can be used as an additional indicator when analyzing the financial efficiency of the company by deriving the result which is different from the theoretical judgment that the superior financial stability index is usually more efficient in terms of financial efficiency. The DEA model used in previous researches is difficult to analyze the financial efficiency by reflecting the output characteristics of the downward indicator that the financial efficiency becomes lower as the value becomes higher like the debt. In this study, we focused on this point and analyzed the efficiency by defining it as harmful output which negatively affects the business performance such as debt among the output. In the future, we will be able to present direct efficiency improvement direction and target value to the manager through the analysis of relative financial efficiency ratio presented in this study.