A method of evaluation of six components of grain strain in polycrystalline metal was proposed. In the present method, the electron backscattered diffraction (EBSD) technique and the digital image processing were efficiently combined. Four components of grain strain, ε_x, ε_y, ε_z and γ_xy were evaluated based on the change in average aspect ratio of the number of pixels inside the grain which was obtained by an optical microscope and digital image analysis, where xy-plane is set on the specimen surface and z-axis is directed perpendicularly to the surface. The other two components, γ_yz, γ_zx, were calculated by taking into consideration the restriction of plastic deformation of each grain which was derived on the assumption that the plastic deformation occurred by crystallographic slipping on a single set of slip plane. An angle of the slip planes was 3-dimensionally identified by observation of the slip line by a scanning electron microscope and EBSD technique. Grain strain of polycrystalline copper during tension was evaluated by the proposed method and the results were discussed from the viewpoints of the distribution of grain strains and the deformation restriction by neighboring grains.