Mutual stocks holding is based on continuing business relation peculiar to japan and built up through a reciprocal transaction. The speciality of mutual stock holding in business groups is from organizations which are easy to be conducted the reciprocal transaction. However, It has been continually decreasing after 1990 that the mutual stock holding rates of the businesses which have special mutual stock holding. The main causes are usually change of system, change of business recognition to the risk of stock holding and change of relationship between businesses. The change of system is seen as the most direct cause of rapid decreasing mutual stock holding. However the most fundamental cause can be said that rapid decreasing of reciprocal transaction based on continuing business transaction made mutual stock holding. It actually means the lost of business groups` essential function that the rapid decreasing of mutual stocks holding which is the representative symbol of business groups` unity and the reciprocal transaction based on the continuing transaction which is business groups` purpose. Such changes of the business groups which are root of japanese business system suggest over all big changes of business relation in Japan which has the peculiar of continuing business relation. the continuing transaction relationship between businesses have various effects but form closed market as one oh the big problem. The such change of Japanese business groups after 1990s is said that japanese market has been rapidly changing to open market.