This paper has attempted to analyze the site planning theories of Raymond Unwin (1863-1940), who is called the father of British town planning. A prominent contribution of his was to establish both the site planning of garden suburb and urban housing style in British type. Here it attempts to analyze how he greatly and firmly established the concept of Housing Group, and how he got this the concept from the life and spatial composition of villages. It could be pointed out that the main factors of the Unwin theory are social mixture, creation of community consciousness and informal landscape design, and that the small enclosed space with plenty of amenity is his main theme. It is pointed out that the Unwin theory is composed of recognizing urban life as totality, and group planning theory, and that he definitely originated a new technique: Housing Group. It is analyzed that the syntactic relations between the group planning theory and housing designs in the English garden suburbs are epitomized in Hampstead Garden Suburb, Middlesex.