To clarify the visual effects of room interior with wooden materials on humans, pulse rate, blood pressure, and brain activity were measured while the subjects were exposed to visual stimuli using actual-size model rooms. The wood ratios (the ratio of the area covered with wooden material to the whole area of the ceiling, walls, and floor) of the rooms were 0%, 45%, and 90%. Subjective evaluation was also conducted. In the 0% room, diastolic blood pressure decreased significantly, but the observed change in the autonomic nervous activity was relatively small. In the 45% room, a significant decrease in the diastolic blood pressure and a significant increase in pulse rate were observed. This room tended to have the highest scores in subjective “comfortable” feeling. The 90% room caused significant and large decreases in systolic blood pressure and diastolic blood pressure at the beginning of the test, but the large coverage of wood appeared to cause a rapid decrease in brain activity and an increase in pulse rate. The present study demonstrated that a difference in wood ratio in the interior caused different physiological responses, especially in the autonomic nervous activity, by using actual-size rooms for the first time.