Strain gauges are frequently used for inspecting the strength and reliability of actual structures. However, the measurement of actual structures by strain gauges needs dangerous works such as pasting strain gauges and cabling them to strain meters located in a remote place. Therefore there is a growing demand for developing non-contact and accurate deformation and stress measuring technique of structures.The authors developed a non-contact and accurate deformation and stress measuring technique using the sub-pixel digital image processing method. This paper presents the detail of the measuring technique and the method of analyzing the measured data, and the results of performance test of the measurement system. The results of the numerical computation and the experiments demonstrated the effectiveness of our deformation and stress measuring technique using the sub-pixel digital image processing method.