We have studied thermal environment in real-scale atrium. The heat budget of the room air and each surface of the indoor walls are examined from the measured temperature and so on. The room temperature is analyzed with the macro model. The following conclusion are obtained. (1) The error of total heat budged was about 5 percent of the total solar incident, so that the data obtained here are very effective to verify the mathematical analysis. (2) The heat gain from the structural frames is a very important factor for designing the atrium's indoor environment.
