The purpose of this paper is to make clear the actual conditions of the transition of motive power in factories in 1912-1920. Examining the factory data of the Statistical Yearbooks of Hiroshima Prefecture, I found the following facts. First, the number of factories using motive power and also introducing electric power increased considerably in 1912-1920. Second, the number of factories using gas engines increased remarkably in 1915 and 1920. The main factor for that was the drastic fall of the relative price of gas rates as compared to the price of coal, oil and electric power. Third, the number of factories using electric power was higher in Hiroshima City and Kure City areas than in other areas in Hiroshima Prefecture. The main reason for that difference was that those areas were supplied with more electricity than other areas.