A fuel production method and a fuel production apparatus, for producing fuel by which the fuel efficiency can be improved and the generation of hazardous substances can be easily suppressed and which is stable, and fuel oil produced by such a method and apparatus are provided. This improves the satisfaction of users, and contributes to the prevention of environmental destruction.A fuel production method for producing fuel oil by mixing and reacting enzyme water with petroleum-based hydrocarbon oil is provided, the enzyme water being produced by mixing a natural plant enzyme, containing at least lipase, in water. The natural plant enzyme further contains cellulase. The enzyme water further contains methanol.