To provide a lower backing plate sheet for perforating a flexible printed wiring board by which the tip of a drill is not damaged and efficient perforation can be highly accurately performed by suppressing burrs of copper foil of the flexible printed wiring board.

The lower backing plate sheet for perforating a flexible printed wiring board includes a thermoplastic resin film with a thickness of at least 100 μm. An ultraviolet-curing resin layer with a thickness of ≥ 5 μm may be formed on the surface of the lower backing plate sheet for perforating a flexible printed wiring board. Metal foil may be overlapped on the surface. The metal foil may be integrally stuck or thermo-compression bonded by a thermoplastic resin film synthetic resin. The lower backing plate sheet for perforating a flexible printed wiring board is arranged to the lower part of the flexible printed wiring board and drilled by a drill from above.