The object of this paper is to attempt an analysis of the process in which securities companies came to underwrite colonial securities and the place of them in the capital market in interwar Japan, focusing on the Chosen Railway bonds. The Chosen Railway, by issuing bonds, was able to pay back the loans to colonial banks. While securities companies underwrote them, colonial banks could call in the loans from the Chosen Railway. The 5th and 6th bonds were profitable for Yamaichi Securities Company as an underwriter and for investors who could receive interests secured by the colonial government grants. The investors consisted of mainly the zaibatsu and financial institutions in the provinces.