This experiment was to investigate the stomatal aperture of wheat variety "Chokwang" grown in two different nitrogen levels. Stomatal aperture was measured at the maximal tillering, shooting, booting, flowering and grain filling stages. Stomatal aperture in leaf blades gradually increased in accordance with the successive leaf growth. The maximal opening of stomata was observed at flowering stages and around noon in a day, but stomata closed around six o'clock in the afternoon. Stomata opened wider in high nitrogen application than in low nitrogen and their effects were highest at the booting and flowering stages