To provide a piping gap closing sheet for allowing easy serial work such as mounting work on a pipe located at a high place while effectively preventing the leak-off of mortar between the outer peripheral face of the pipe and itself by increasing an area of attachment/adhesion to the outer peripheral face of the pipe, and to provide its method.

The piping gap closing sheet comprises a closing part 10, a bent part 20 consisting of a plurality of tongue pieces 21, and a belt part 30 connected to the bent part 20 and wound and adhered onto the outer periphery of the bent part 20 adhered to the outer peripheral face of the pipe.