PURPOSE: To efficiently produce a hydrocarbon fuel suitable as a fuel.

CONSTITUTION: (a) A mixture of carbon monoxide and hydrogen is brought into contact with a hydrocarbon synthesis catalyst at elevated temperature and pressure to prepare a substantially paraffinic hydrocarbon product. (b) The obtained hydrocarbon product is brought into contact with hydrogen in the presence of a hydroconversion catalyst under a condition such that substantially no isomerization or hydrocracking of the hydrocarbon product occurs. (c) At least a part of the hydrogenation product of the step (b) is brought into contact with hydrogen in the presence of a hydroconversion catalyst under a condition such that isomerization and hydrocracking of the hydrocarbon product are caused to produce the substantially paraffinic hydrocarbon fuel.