The purpose of this study is to interpret a house as material into culture. Main method is an ethnographic interview with dwellers as a part of a participant observation, a kind qualitative study. Significantly two different types of folk housing are discovered in East and West areas of the Cheju Island. In the East, kitchen itself forms a separated building, Jeongji-gori, whereas in the West, kitchen is within a main building, An-gori. Different type of kitchen is formed by the different family system. While independent family system of son and father selects a separate kitchen building as a general rule of Cheju Island, an extended family system between father and son selects same kitchen, Jeongji-gori, in the east area. Natural environment of infertile soil of east area makes family work together and eat together. Inner space of the kitchen building is utilized not only in cooking but also in eating, working, and sleeping. In order to explain folk house type, a 'culture area' concept is suggested. The interrelated 'cultural type' of architecture behind a physical surface 'type' is suggested as a new typology.