Intrapersonal intelligence refers to the ability to understand one's own emotions and potential, control oneself and design one's future. It has been seen as being important as it provides a motivating effect to activate other intelligences in Multiple Intelligence and is an important form of intelligence for self-actualization. However, an intrapersonal intelligence assessment scale is insufficient when it comes to measure intrapersonal intelligence independently because research into intrapersonal intelligence is still in its infancy and research data and evidence in this area remains scarce. The purpose of this study is to verity the factors of intrapersonal intelligence and develop an intrapersonal intelligence assessment scale for adults. The results of the research were as follow: First, intrapersonal intelligence consists of the four factors which are self-understanding, self-planning, self-control & utilizing and self-reflection. Second, the four factors and 36 items developed for the scale have been extracted from the exploratory factor analysis. Good-fitness of the four factors structure and the 36 items proved to be valid through confirmatory factor analysis. Additionally, the results of criterion validation indicated that all four factors of intrapersonal intelligence were highly correlated with K-HAPI and K-MIDAS. The reliability was also statistically significant. As the above results show, this study into intrapersonal intelligence provides fundamental data to help adults to understand and regulate themselves, design their future and self-actualization. It can also be used as a measurement tool to assess programs related to intrapersonal intelligence.