Abstract.A lighting control method has been proposed which adjusts the circadian rhythms of office workers and eliminates a decrease in the arousal level in the afternoon by exposing a high intensity of light in the morning in order to improve their productivity. As a result, it was found that the task performance of the CPTOP test under 2,100 lx was significantly higher than that under 700 lx and more than a 9% improvement of task performance was achieved. Furthermore, a demonstration experiment has been conducted in order to confirm the effectiveness of the proposed lighting control method in actual office rooms. As a result, it was confirmed that the performance of their accounting work was over 10% higher than under normal conditions.