����The main purpose of this study is not only to clarify the thinking mechanism in architectural design process due to professional architects by means of sketch but also to analyze the differences with regard to developing or dealing with building spaces in planning between them and students majored in architecture. From above point of view, we have recorded a series of their design process on video tapes. Through surveying the tapes, we discovered that professional architects are not always paying attention for whole design of the building but also considering accompanied details of the space. In other words, the professionals have been conscious of the relationships of many factors which composed ��������������������������������������������������������������������������������������������������������������������-plicitly hidden requirements compared to those students makes a plan to be optimum or exquisitely.