This study was carried out to investigate the effect of the red light on embryo tissue of barley during germination. The solubility of starch in endosperm of germinated barley was different between dark and red treatments at the 3rd day of germination, but was increased by the red light from the 4th day of germination. Blue value of the starch in the germinated barley decreased rapidly from 0.42 at the 1st day to 0.13 at the 6th day in the dark, and same tendency was found in the red light, but blue value was lower in the red light than in the dark. Aleurone cell wall was swollen much faster in the red light than in the dark during germination. The cell wall was broken down more greatly in the red light than in the dark at the 5th day of germination.