The paper shows the result of fundamental experiments it applies the blended fuel of soybean oil which is producible vegetable on and kerosene to the diesel engine for the purpose of the reduction of the fossil fuel use. The mixing rate of the blended fuel was made to be soybean oil 20〜80vol%, and tried the application with them to the current diesel engine. As a basic experiment, the property of the fuel was examined in the beginning, and the ignition experiment was carried out, and in addition, the spray experiment of the spray distribution in the pressure vessel was done. As the result, it was possible to obtain the good result over the expectation with heating of the 20 and 40vol% blended fuel.