PURPOSE: To obtain a uniform and stable emulsion fuel for contributing to the save of energy, by blending an oil with water and an emulsifying agent with stirring by a line mixer, mixing further water drops in the emulsion with it finely and uniformly.

CONSTITUTION: An oil such as heavy oil, etc. is quickly blended with water and an emulsifying agent with stirring by the line mixer 5 automatically while the flow rate of the blend being controlled by the control device 2 connected to the flowmeter 1 for oil amount, to give a heterogeneous w/o type emulsion having fairly large water drops in the oil. The emulsion is further homogenized and made fine by the homogenizer (or colloid mill) 6 so that the water drops in the oil are processed into about 1W2μ, to give the desired emulsion fuel.