Recently, because the micro-machine is noticed and electronic equipments are made much lighter and smaller, the demand for micro materials is increasing. The researches for evaluating the mechanical properties of micro materials have been carried out. However the reliable data of the micro materials is insufficient, because the standard evaluation method of micro materials has not been established. In this study, the steel fine wires of austenitic stainless steel Type SUS304 were used as the material. Its diameter was 30, 50, 80, 200μm. The tensile strength tests were carried out. As the results, and Young's modulus increased with decreasing the diameter of specimen. Young's modulus got from linear sensor extensometer was corrected by JIS R 7606. This corrected Young's modulus was almost equal to Young's modulus calculated from the elongation of specimen by direct contact extensometer. Also, it was seen that the tensile strength increased with decreasing the diameter of specimen, and that the dispersion of the tensile strength increased with decreasing the diameter of specimen.