"Kasaku Tatekata Jomoku" is important as germination of the .modern building codes system in Japan. This paper investigates the enacting conditions of this code, and reports the following points. (1) Kanagawa Prefecture was aiming at the promotion of urban sanitation, mainly owing to a proposal of D.B. Simmons (1872). (2) Kanagawa Prefecture put an urban renewal project into practice in 1873 as a part of (1), and enacted "Kasaku Tatekata Jomoku" as the building rules of the new urban area. (3) I am convinced that the governor, Oe chiefly promoted enacting this building code.