We have been developing a borehole stress measurement system using electric speckle pattern interferomentry (ESPI). The system was designed to be small size and light weight in consideration of mobility in field to measure crustal stresses by means of the strain-relief method. Moreover, the system is able to measure quantitatively out-of-plane deformations (radial deformations) of the cylindrical area in a borehole in terms of the half of the wave length of Laser light. In laboratory tests, we obtained results which confirm ability of the system to be used for precise stress-strain measurements.