This paper explores the flow of fund around the holding company (headquarters) of Mitsubishi Zaibatsu during the Second World War. From the late 1930s, the Mitsubishi holding company started to raise fund from the outside capital market through selling the shares of its affiliated companies, and invested the fund to other affiliated companies. In this sense, Mitsubishi Zaibatsu was no more a semi-closed internal capital market as it used to be. In 1940, the holding company took another step, namely, public offering of its own shares. After that, while raising fund more from the outside market, it invested to wider range of firms. From 1943, a new phase started, where the affiliated companies raised fund directly from the outside market, not through the holding company.