The main purpose of this paper is to assess the effects of the geographic expansion and contraction(i.e., increases and decreases of bank branches) on bank efficiency by using DEA(Data Envelopment Analysis), FDH(Free Disposal Hull), and Regression Method. The procedure is as follows: First, the productive efficiency of 108 Korean banks for 6 years (1995~2000) using DEA and FDH methods will be measured. Second, the increase and decrease of bank branch numbers and efficiency change for each year and each bank will be investigated. Third, the regression analysis will be done for confirming the relationship between bank branch numbers and efficiency. Lastly, 4 hypotheses will be tested regardings the above-mentioned results. The empirical findings are as follows: First, increase of bank branch numbers enhanced the efficiency about 50% of bank branches. Second, contraction of bank branch numbers did non increase the efficiency. Third, before IMF supervision system, increases of bank branch numbers increased the efficiency, however, after IMF system, efficiency was decreased. Fourth, regression results show that expansion of branch numbers will decrease the efficiency, and contraction of branches and small office will decrease the efficiency.