This paper presents a basic research on a measurement of strain in the bulk of materials by using high energy white X-ray from a synchrotron radiation source of SPring-8 in Japan. A high-tensile strength steel (JIS-SHY685) was used as a specimen loaded with bending. Strain distribution in it was evaluated by the energy dispersive method using diffracted X-ray transmitted through the specimen. As a result, the internal strain of high-tensile steel of 5, 10 and 15 mm thickness could be evaluated using white X-ray which range of energy from 50 keV to 150 keV. The measurement with a high degree of accuracy was accomplished using α-Fe321 diffraction in this material. The results showed that the internal strain measurement in the depth of the order of millimeter using the high energy white X-ray is practicable at SPring-8.