An object of the present invention is to provide a novel method for effectively utilizing energy in a waste-incineration facility annexed with an ethanol production equipment that is capable of achieving a further enhancement of the energy recovery rate.The present invention is a method for effectively utilizing energy in a waste-incineration facility annexed with an ethanol production equipment that forms bioethanol from carbohydrates contained in biomass of municipal solid wastes, comprising: an ethanol production step of mixing a part of heavy components containing garbage and wet papers with pulp separated from light components containing dry papers and plastics, all of which are obtained through a pretreatment of the municipal solid wastes, and fermenting the mixture； and a methane production step of fermenting a balance of the heavy components and/or a distillation residue generated in the ethanol production step.
