In this study, we estimate the NNI(Nearest Neighbor Index) which is considered altitude of rain gauge network as a
method for evaluating appropriateness of spatial distribution and the current rain gauge network is evaluated. The
altitude is divided by equal-area-ratio and optimal NNI within given basin condition is estimated using harmony
search method for considering geographical conditions that vary from altitude to altitude. After calculating current
state and optimal NNI for each altitude, the distribution of the rain gauge network is evaluated based on the
difference between the two NNIs. As a result, it founds that the density of rain gauge networks is relatively thin as the
altitude increases. Furthermore, it will be possible to construct an efficient rain gauge network if the characteristics of
different altitudes are considered when a new rain gauge network is newly constructed.