In this report we aim to clarify collective form of housing units expressed by exterior building elements. It is one of the important subjects which decides the compositional characteristics of collective housing, that is how to make the spatial units and how to combine them. First, we classified the building elements which compose the external form, and we found diachronic tendency of elements in examples. Secondly, we defined the compositional units in external form through analyzing the relationships between the building elements and housing units. Then we found typological compositions in collective housing. Through comparing these compositions, we found some characteristic collective form of housing units expressed by building elements. We think these results are structural framework of the exterior composition of collective housing.