A segment is coupled to another segment in circumferential and longitudinal directions thereof to assemble a rehabilitating pipe for rehabilitating the existing pipe. Each of the coupled segments has at least one coupling surface provided with a recessed part that confronts the recessed part at the coupling surface of the segment to which it is coupled to form therebetween a gap that is configured to receive and hold waste material existing at a bottom surface of the existing pipe when the rehabilitating pipe is assembled inside of the existing pipe.