To increase the protein concentration of wheat grain, we applied nitrogen fertilizer at 10 days after heading and examined its effect on agronomic characteristics and flour quality. This top dressing did not affect the agronomic characteristics except for delaying of the ripening stage, but increased the 1,000 kernel weight and test weight. Protein concentration increased linearly as the amount of applied fertilizer increased, at a rate of about 0.5% per 1 gm^-2 nitrogen top-dressed. Gluten concentration increased as the protein concentration increased, irrespective of cultivar, breeding line and year. There was a significant negative correlation between protein concentration and flour color. As the protein concentration increased, flour color became gray. Nitrogen fertilizing at 10 days after heading effectively increased the protein concentration in wheat.