The goal of this paper is to understand the visual information process and the characteristics of behaviour of the architectural design process using visual protocol analysis through the actual experiment by the architect. The visual protocol analysis is developed on the basis of the theories of the visual information processing model and visual mental image, which can explain visual representation in architectural design process. A protocol study is reported in which the experimental data by architect is analyzed through the protocol analysis method. The whole design process is divided into the stage of 9 tasks which are classified into 18 visual representatiov. The results about visual cognition in cognitive science are reviewed and summarized, and these findings will help understand the architectural design nature.