Owing to a space covered by glass, atrium is an attractive space with a possibility as an inner public space but a typical building type with a high-energy load. From the aspect of global environmental issues, to reduce energy load is an important assignment to solve. Contriving a planning guideline of an opening is considered as the most effective environment adjustment method, to offer a highly assessed amenity space and secure openness to outside, keep the energy load to a minimum, and apply the natural energy such as daylight to a maximum at the same time. Users' assessment of environment was performed by questionnaire survey, then the structure of users' assessment was analyzed and design condition was regulated by multiple regression analysis. The opening design guideline to offer a highly assessed space was proposed with concrete environment adjustment method.