The authors investigated an office building in Japan incorporating energy-saving features and environmental technology. The building is medium-sized and incorporates two air-conditioning systems: a natural ventilation system and radiation air-conditioning system. The temperature environment of the building and its psychological effects on office workers were surveyed using a questionnaire. The measurements of the natural ventilation system were made in 2016. The natural ventilation system of this building reduces the indoor temperature by first opening the window. The ceiling uses the heat storage capacity of concrete to retain a low temperature in the room during the night. Air flows through the room with the natural ventilation system. Further, various problems occur because of noise, and the building has a constantly fluctuating environment. However, according to the results, even in such a natural ventilation system in which the indoor environment changes, office workers are able to conduct business without much dissatisfaction.