Abstract
The author proposed a theoretical model of design thinking based on psychologist Vigotsky's theory. Design thinking is typical human problem solving style by creating tools as means for problem solving. Core of design thinking is searching process for new means that has suitable function to meet the goal. It is taken in trial-and-error representation process of means, in which repeated expression of subject’s inner image to externalized form of it. Creative thinking appears in this process. It is, however, in paradox that, in spite of it is in focused goal-oriented thinking, it needs widened search space for divergent thinking. In that situation an external stimuli can make the searching space wider, because the external world which includes designer's sketch is always larger than designer’s searching space.
