What is the trial-and-error process of design thinking? Hisataka Noguchi When we think about design creativity we should recollect the fundamental feature of the design thinking process as this: (1) Design thinking is essentially included in general human productive works as a whole. (2) Design thinking usually goes not straight to the goal but requires trial-and-error processes in which repetitive divergent and convergent thinking are taken. (3) For converging the trial-and-error to goal, designer needs self-evaluations in every step of getting tentative solutions. (4) Even though the collective thinking and discussions facilitate this process, creative result can be carried out basically depend on each designer's self-evaluation. The author tried to make a model of trial-and-error process of design thinking in which one can analyze how the self-evaluations converge the process as a representation of designer's internal world.