This paper reports the models of the designer’s thought process based on a protocol analysis from the viewpoint of design information structure and its formation process, which can be a fundamental part of practical design support tools. A series of four design meetings in a company, with intervals of several weeks, were observed to derive these models. The models consist of information elements derived from the cognitive design problem-solving process, and represent the conceptual design process by the derivation relationship among the information elements. The scenario is considered as an important information element to promote the evolution of product design. The proposed models are proven by protocol analysis with statistics and a transitional view of the coding scheme based on the models.