A reinforcing material-having functional sheet which comprises a sheet-like functional material comprising a functional
powder and a binder resin and, laminated thereon, a reinforcing sheet comprising a
woven fabric or a non-
woven fabric, which are bonded, wherein the basis weight of the reinforcing sheet, the
fiber diameter of the
fiber constituting the reinforcing sheet and the functional sheet thickness are in specific ranges. A sheet-like
electrode for electric double layer capacitors which
electrode comprises a sheet-like
electrode of carbon
fine powder and a
fluorine-containing
polymer resin and, laminated thereon, the reinforcing sheet, and an
electric double layer capacitor having this electrode. The functional sheet has strength and no
elimination of the functional material
powder, and also efficiently exhibits high functional properties. The sheet electrode can efficiently prepare electric double layer capacitors having strength, remarkably low
internal resistance, slight lowering of charging and discharging capabilities, excellent durability and long lifetime.