The purpose of this study is to examine the development of the sector plan in Alavar Aalto’s works of architecture. The analysis of those works has made it clear that the the sector plan varied from work to work and it gradually lost its characteristics to finally approximate to the rectangular plan. In this process, the appearance of the buildings became simpler while their interior spaces in which the architect seemed to have found more importance became more complex. The fact that the sector plan continued to be used even for different types reveals that Aalto pursued all the possibilities that the sector plan could offer.