The purpose of this study was to analyze how teachers’ learning was promoted through community collaboration in the learning through working group of a special needs education high school for students with intellectual disabilities based on the concept of community of practice in Wenger et al. (2002). This case study examined a period of three years at B Prefectural Special Education School in A Prefecture. Consequently, four characteristics of this case were clarified. First, because the community was smoothly launched by involving superiors, the community of practice immediately developed from “potential” to “coalescing”. Second, the work-study group promoted learning in a “double-knit” organization, due to an appropriate sense of distance between the community of practice and team. Third, the presence or absence of practice (a socially defined set of methods) relates to community development. Fourth, the existence and connection of coordinators and thought leaders were necessary for the maturity of the practice community. The existence of community librarians is considered important for future development.