The Sato Semi-dieseel Engine is very unique engine in the history of the manufacture of the engine in Japan. This small farm engine heats hot tube by charcoal fire, Running by the aid of light oil as fuel. It was designed and manufactured by Chujiro Sato of Simane prefecture in 1931. With this paper we report. the history and structure of this eingine, based on our industrial archaeological research of the most early period model discovered by us recently.