A power demand regulation system has a power demand regulation device that regulates the load applied to equipment of an electrical power system by a load apparatus operating by means of power from the electrical power system, which supplies power to consumers. When regulating the load to the equipment, the power demand regulation device selects a load apparatus as the subject of a request for an alteration of operating state on the basis of by-apparatus load information, which is information of each load apparatus, and a regulation target value, which is the amount of load that is to be regulated, and, in the period from the start to the end of regulation, executes a plurality of times the outputting of an alteration request that requests the alteration of the operating state of the selected load apparatus.