PURPOSE: To measure strain precisely and quantitatively by utilizing correlation between the number of electron channeling patterns and the strain.

CONSTITUTION: In general, when an angle of incidence is varied while an electron beam is caused by a scanning electron microscope to strike a crystalline conductive material, such as a metallic material, at one point, an electron channeling pattern appears. This pattern loses contrast when a sample is distorted, so a sample free of strain by sufficient annealing and another sample having prescribed strain are used and the number of pattern lines crossing a prescribed circle drawn on a pattern image is counted. Then, correlation between the number of the lines and the strain is found. This relation is linear, so that the extent of strain is found from said number of lines.