There are various kinds of Large-Scale apartment sites in Seoul. There are more households in apartment sites than single family houses. Nowadays, it is easy to find a lot of apartment sites built in the style of a high rise building. On the matter of space, a building is influenced by the buildings near it. The influence a building has to another is different in both qualitative and quantitative ways. Therefore, in the case of apartment sites, the environmental surroundings of each household is affected by the nearby buildings. For these reasons, the environment is having more and more influence on the price of each household in apartment sites. This paper has defined Sunshine and Sky as the major environmental elements. In order to be analyzed, they have to be measurable. Thus, there are two types of variables in environmental surrounding of apartment sites, -the Duration of Sunshine and the possible amount of visible Sky- the significant variables which influence the housing price. This paper deals with the relationship between the possible duration of sunshine and the possible amount of sky a household is visible to. It focused on 62 different apartment sites which were built after 1990. It is based on the 3-dimensional Geographic Information System & Computer Aided Engineering for analyzing the sunshine simulation and the viewing simulation. This paper will be helpful for designing the apartment sites considering the balance between sunshine and sky.