The purpose of this paper was to discuss critical issues of 30% reduction and introduction of the contents for new Mathematics Curriculum at middle school in Japan in 2002. This paper consisted of three part: (1) The contents of the new mathematics curriculum in middle school in japan. (2) Discussion about critical issues of 30% reduction of the contents for new Mathematics Curriculum. (3) Proposal of the point of view about 2000 mathematics curriculum in Korea. The authors pointed out that the reduction of the mathematics curriculum in Korea should be considered of a true reduction more carefully.