Analysis of wood structure was carried out using laser diffraction. The arrangement and average diameter of tracheids and fibers was observed from the laser diffraction pattern at cross section, and the average diameter of tracheids and fibers was also examined by microscope. Results were in approximate agreement. Generally, laser diffraction figures of soft wood were shown more clearly than those of hard wood, and arrangements of the tracheids and fibers were orderly in the radial direction compared with the tangential direction. Variations of the average diameters of trachieds were measured from the pith to the bark at cross section of Sugi wood. (Author abstract, modified)