The purpose of this study is to verify the existence of spatial autocorrelation between the domestic airports in Korea and to examine the spatial effect on the efficiency of airports by using a Spatial Stochastic Frontier Analysis(SSFA). The output variables of airports' efficiency were considered with both the operation performance and the customer service performance to evaluate the efficiency with quantitative and qualitative performance aspects. The sample of this study are 11 regional airports out of a total of 15 regional airports in Korea. The annual data from 2014 to 2018 were gathered from the statistic data of Korea Airports Corporation and Ministry of Land, Infrastructure and Transport. The results show that spatial autocorrelation on the quantitative efficiency did not exist, but qualitative efficiency existed. It indicates that the qualitative efficiency is influenced by the distance between airports. More specifically, the results of SSFA show that the qualitative efficiency would be increased by the distance between airports is getting shorter. It implies that the cluster of airports would be an important factor to increase a qualitative efficiency because the closer distance between airports makes more competitive to attract customers, thereby airports would strive to improve customer service. In conclusion, this study provides a useful information to establish the strategy for reinforcing airports' competitiveness, as well as national policy for opening new airports or expanding airports.