A method for producing an activated carbon sheet having high electrolyte impregnation capacity and high mechanical strength is provided. The method for producing an activated carbon sheet includes a sheet preparation step of preparing a sheet including an activated carbon, an electrically conductive carbon material, and a fibrous fluorocarbon resin binder, which fluorocarbon resin is polytetrafluoroethylene and/or modified polytetrafluoroethylene; and a light irradiation step of performing light irradiation of at least one side of the sheet such that the cumulative irradiation dose on the sheet surface is 50 to 1000 mJ/cm2.