This reseach is focused on the formative period from zaibatsu to enterprise grouping (it is not a vertical group but a horizontal group). After World War II, the zaibatsu dissolution was carried out by Occupation policy. In Mitsubishi zaibatsu, Iwasaki, owner family were removed from the firms, and Mitsubishi-honsha, which was a holding company, was broken up. Without owner family and a holding company, operating companies had been forming a new style of business grouping. The new grouping was consisted of autonomous companies. So it was necessary to have the function of maintaining a body of grouping. But then, it was not long before all of top managers were promoted in their companies. So almost of them did not have enough management skill and experience for interests coordination among a member of the group. Therefore senior managers, who used to be superior to top managers and obliged to retire after World War II, executed the function of interests coordination instead of them. In 1950's, it was senior managers rather than mutual stock holdings and top managers committee among a member of the group that fulfilled the function to band together in Mitsubishi group. And it depended upon human relationship among top managers and senior managers, which was built in the period of the zaibatsu.