Power demand control is performed without a decrease in productivity. A device for performing electric power demand control includes: a processor; and a storage medium including an instruction for causing the processor to obtain a sum of energy consumption of a plurality of manufacturing devices, obtain a production capacity from production information on each manufacturing device, and perform electric power demand control on a manufacturing system based on the production capacity and the sum of energy consumption. To perform electric power control includes determining that electric power demand control is necessary if the sum of energy consumption reaches a predetermined threshold and excluding one of the manufacturing devices having a smallest production capacity from a target of electric power demand control.