In this study, monthly and annual aridity indices which are the ratios of precipitation to potential evapotranspiration in Seoul climate measurement station were analyzed for past 50 years (1961~2010), and the ratio of aridity index simulated by climate change scenarios (RCP 4.5 and 8.5) for each future period (2011~2040, 2041~2070, 2071~2100) to aridity index for the past period (1971~2000) was analyzed. Furthermore, 5 different potential evapotranspiration equations (FAO P-M, Penman, Makkink, Priestley-Taylor, Hargreaves) were applied to analyze the effect of potential evapotranspiration equation on estimating aridity index and aridity index variation ratio (%). The study results indicate that the monthly precipitation, average temperature and potential evapotranspiration were increased in each future period as compared to past period for both RCP 4.5 and RCP 8.5. Furthermore, winter period showed more significant increase of potential evapotranspiration than summer period, but aridity index showed different patterns as compared with potential evapotranspiration reflecting the influence of precipitation. Therefore, it is necessary to make preparation for the increment of winter evapotranspiration in terms of water resources management. The monthly and annual aridity indices based on future climate change scenarios were greatly different according to potential evapotranspiration equations; however, monthly and annual patterns of aridity index variation ratio (%) in the future period as compared to past period were very similar regardless of applied potential evapotranspiration equation.