In problem solving, some learners make mistake at understanding of problem, so this process can be considered as an important target of support. However, this understanding process tends to be unclear in usual practice, and it is difficult to see this process. For this difficulty, “Externalization” is taken as one of countermeasures.In this paper, we propose the concrete method to realize the environment for externalization at problem solving of mechanics of high school. Also, for this realization, we are designing and developing the computer system. Through experimental use of the system, we have confirmed that subjects could express their understanding with the system and they thought their activities on the system were useful for learning.
