This paper focuses on the idea development as a creative thinking process for design innovation. The process of thinking has the thinking structures of abduction and transformation. After we had studied the design thought, we found a structure of a thinking system, and created a creative thinking model with this. Using job analysis, we examined the duster of design jobs, which form the design process, and verified the thinking model. The findings suggest that our idea development has the creative process not only of divergent thinking and convergent one, but also of transformation in design. In same time, the design thinking shows their pattern of transition from abstract concept to concrete object. Between the design jobs, idea development shows higher difficulty than other jobs - marketing, product planning and follow-up. Combining the D-T-C (Divergent-Transformation-Convergent) thinking with abstract-concrete thinking, we designed a DFD(data flow diagram) for an early model of computer mediated thinking system (CMTS). This has implications for design support.