Natural stress measurements have been made at two sites at the depth of 280m from surface by means of stress relief overcoring methods using three directonal deformation gage. Attempts have been made to determine the state of natural stress in the rock and provide useful basic data to investigate the stress distribution and the determination of yield zone around powerhouse cavern. The magnitude and the direction of the miximum principal stress obstained from in-situ stress measurements is -96.1kgf/$ extrm{cm}^2$ and N38$^{circ}$W, N35$^{circ}$W respectively. Vertical stresses are in approximately agreement with the theoretical value. The ratio of measured to theoretical stresses are 85% at two sites. The ratio of average horizontal to vertical stresses(k=($sigma$h)ave/$sigma$v is 1.07.