This paper compares and examines the institutionalization in juvenile reformatory for a month in Korean and the special short-period treatment in Japan, and simultaneously explores problems with the institutionalization in juvenile reformatory for a month in Korean and a plan for their improvements while considering problems raised in Japan.The results of the comparison between the institutionalization in juvenile reformatory for a month in Korean and the special short-period treatment in Japan can be summarized as follows. ⑴The special short-period treatment in Japan has concrete criteria about subjects compared to the institutionalization in juvenile reformatory for a month in Korean, and ⑵is carried out over the whole areas in Japan. ⑶Also most of the contents of the program are implemented by some external entrusted agencies as is not the case in Korean, and ⑷the Japanese program makes the least interventions in all of the component including education. However, the number of subjects to the Japanese program continues to decrease due to the insufficiency in the treatment based on juvenile delinquents characteristics, the over burdened staffs, the criticism about educational effects, and the problem of the stigma of the experience in juvenile reformatories.The institutionalization in juvenile reformatory for a month is one of the most innovative system among the institutional treatments, and hence expectation about its effectiveness is high while also the same extent of concerns exist.As one can understand from the case of the Japanese short-period treatment, in order to constantly obtain the effects meant by the treatment No. 8, we should, first of all, concretely specify subjects, generally examine the characteristics of and problems with individual subjects, and build various educational programs accordingly.