This paper addresses how inclusive education under collective culture is possible. Inclusive education, which more-or-less involves changing the current schools, has been denied, doubted or distorted by both policy-makers and practitioners of general and special education in Japan. Main reason for the setback in inclusive education can be explained by assumed homogeneity and value of harmony in Japanese schools; children with apparent difference could be easily excluded or alienated under collective Japanese culture(Tsuneyoshi 2001). However, there are in fact some schools in Japan which appear to carry out inclusive education regardless of the setbacks above. Using the qualitative data collected by fieldwork and interviews at an elementary school with inclusive practice, this paper discusses what the critical part of the school to manage the inclusive practice without support from policies and/or precedent practical models. According to Skrtic (1991), educational institutions in general maintain two-dimensional bureaucracies(machine and professional), which prevent them to change for including everybody, and thus "adhocracy", problem-solving-oriented organization, is the key to inclusive education. In fact, the research found that the school maintain "adhocratic" organizational culture instead of professional bureaucracy. In other words, they never categorize children according to ability, ethnicity or social status, but whenever school staff notice any signs of problems, they discuss the matter for a solution yet never do they systematize or designate persons in charge according to type of problems or children. Such "adhocratic" culture is maintained not only by leadership or professional development in school but by parents and people in the community who are encouraged to come to school to support children whenever they can. In fact, the school uses all the diversity and problems in school as educational materials for children and staff to cope with collectively, and thus collective culture does work to solve problems in cooperative manners but never promote to create homogeneous environment which may result in exclusion of some children. [Paper presented at the Inclusive and Supportive Education IV Conference Congresso Internacional da Pró-Inclusão (8th, Lisbon, Portugal, July 26-29, 2016.]