Established by Chikuhei Nakajima in 1917, Nakajima Aircraft Company grew into a huge munitions company during World War II. Together with Mitsubishi Heavy Industries, the Company was ranked as one of the two largest aircraft manufacturers in Japan. At the time of the so-called “dissolution of Zaibatsu”, the Company was named among the significant targets of such measures together with the Four Largest Zaibatsu and divided drastically into pieces. Thus, though important, no study has been made about the Company because of extreme lack of available materials. The purpose of this paper is to clarify the characteristics of the Nakajima Aircraft Group by digging out materials so far unknown, the results of which are as follows: 1) The capital of the Company was usually small and the stocks were possessed actually by the Nakajima brothers alone. The Company was, therefore, able to make decisions promptly, meeting the severe requirements from the military authorities, which led it to realize a great progress. 2) Devoting itself to working only for the army and navy, the Company had been structured not to make any profit except for that necessary to make dividends of 7% p.a. (3) Because of its small capital and small accumulation of profit, the Company was forced to rely extremely on borrowings, and in the stage of its rapid growth during the War, it depended solely on The Industrial Bank of Japan. (4) Although the Company had possessed stocks of many companies or made loans to them, these relationships did not constitute a Zaibatsu, but one of the general cases often seen, where a parent company controls many subcontract companies.