<p>"Design thinking" attracts attention among various fields, and the tool development and the education regarding design thinking are carried out in various places. Their effectiveness, however, is evaluated only by subjective way (e.g. interview and questionnaire), and the way to analyze and evaluate it objectively is needed. This study aims to clarify the prefrontal cortex (PFC) role in design activities using a NIRS device. The experiment measures the brain activation amount between the two sketch tasks: reminding the typical shape and generating new idea of the design object. The Mann-Whitney test shows the right/left dorsolateral PFC and medial frontal cortex (MFC) in most participants were activated during the idea generation task than reminding one. Additionally, to catch the thoughts and emotion during the design tasks, the analysis focused on the design-idea-decision moment and the activated areas: MFC and orbitofrontal cortex (OFC). Although the result confirms few statistical differences, these values at the moment in MFC and OFC are larger than those at reminding task, at the rate of 73% and 65%, respectively.</p>