An intermediate spliced portion waterproofing structure has a first covered electrical wire where an intermediate portion of an insulation sheath is stripped off to expose a lead wire; a second covered electrical wire where an end portion or an intermediate portion of an insulation sheath is stripped off to expose a lead wire, and where a lead wire-exposed portion thereof is electrically connected to a lead wire-exposed portion of the first covered electrical wire; a protective sheet made of a hook-and-loop fastener wrapping an intermediate spliced portion in a state where the intermediate spliced portion is positioned inside a raised fiber-forming surface, the intermediate spliced portion being a connecting portion of the lead wire-exposed portions of the first and second covered electrical wires, and a waterblocking material made of a moisture-curable waterblocking agent that is applied to the protective sheet so as to surround the intermediate spliced portion.