Education for international understanding in Japan was focused to develop its own national identity as well as to recognize its coexistence through intercultural education. Then, we have investigated the opinions of Japanese school teachers in terms of their recognition of the necessary content to introduce school instruction of intercultural education using a questionnaire method. In the questionnaire, 14 items of three principles were extracted from the criteria of UNESCO (United Nations Educational, Scientific, and Cultural Organization). For analyzing the collected data, the geometric mean was used. Subsequently, a one-way ANOVA test and multiple-comparison procedures were conducted. By including teachers in suburban areas in Japan, we obtained 123 valid responses. All items showed a necessary level of geometric means, and particularly items of the first principle "respect cultural identity" and items of the second principle "provide knowledge for participation" showed statistically significant positive necessity levels. However, an answer of "I have never thought" increased in the third principle "provide a chance to contribute" that was closely related to present world concern of global citizenship education and statistically was not significant. From the result of the multiple-comparison procedures of the second principle and the third principle, seven pairs of statistically different items were extracted. Then, we discussed the enhancement between Japan and UNESCO and influence of school environment in Japan.