There is provided a control method of a compression-ignition internal combustion engine capable of easily coping with a wide range of required loads by a single fuel.A compression-ignition internal combustion engine includes a first tank (2) for storing a blended fuel that contains alcohol and liquid hydrocarbon at predetermined percentages and a second tank (4) for mixing the blended fuel supplied from the first tank (2) with water and storing a liquid mixture of the water and the alcohol mixed with each other and the liquid hydrocarbon with the liquid mixture and the liquid hydrocarbon separated from each other, and a supply of the blended fuel stored in the first tank (2) and a supply of the liquid hydrocarbon stored in the second tank (4) are varied according to a required load of the compression-ignition internal combustion engine (1).