In the context of career decision and career development extended to the whole life cycle, the existing career decision motivation scale developed for students does not adequately reflect the adult career decision scene. We approached it, conceptualized it, and developed a measurement tool. We conducted qualitative research on adults with career transition experience, selected 8 representative behaviors taken during the career decision process, and composed 32 questions by responding to each question with 4 motivation types. As a result of exploratory factor analysis for 233 adults, 4 factors were divided by motivation for 32 questions, and confirmatory factor analysis for 240 adults also showed good model conformity. Adult career decision motivations was clearly divided into four factors, external regulation, introjected regulation, identified regulation, extrinsic motivation. In order to confirm criterion validity, the correlation between career self-efficacy and self-esteem was confirmed. The implications of the above results were discussed in terms of the structure of adult career decision motivations and self-determination Theory. A basic tool for adult career research was prepared by developing a scale that measures the perception of individual in adult career decision-making. Adults’ career decision motivations were divided into controlled motives and autonomous motives, but they did not conflict with each other and suggested the possibility that individuals with high motives could exist simultaneously.