The purpose of this study is to understand what kinds of lighting give us visual harmony in a space where both daylight and artificial lights are used. We made a hypothesis that daylight and the artificial light would be harmonious when the overall lighting in the space was described by a compound of the lights from the window and the whole ceiling. For this, we examined under what situation the light from windows and the artificial lights could be in harmony. Subjects adjusted artificial lights and evaluated comfortable lighting environment while considering visual harmony of lighting. We compared the experimental value of illuminance distribution with supposable value by the hypothesis and analyzed the correlation between the subjective evaluation of the visual harmony and the residual of the above two functions.