A manufacturing method of a water emulsion fuel by which the O/W type water emulsion fuel can be reliably manufactured. For this purpose, an initial method of the manufacturing method has a fuel and additive charging step, an agitating step of agitating the fuel and the additive, a water charging step of charging a predetermined amount of water into a mixing tank, a fine processing step of pumping out a mixture solution of the fuel and the additive, and the water to pass them through the fine processing means and returning them into the mixing tank, a separating step of separating the water and the fuel, and an emulsifying step of emulsifying the fuel, the additive and the water by the step of pumping out the charged solution from the mixing tank, passing it through the fine processing means and returning it to the mixing tank.