Thermoplastic multi-walled pipe which has at least two tubular members different in inside diameter and concentrically arranged, these tubular members being spaced and supported by a plurality of ribs so as to provide hollow portions therebetween. The bond strength between the inner end surface of the rib and the tubular member supported thereby is less than that between the outer end surface of the rib and the tubular member supported thereby, so the exposure of the inner tubular member is easily achieved by means of an external force. After exposing the inner tubular member these multi-walled pipes are conveniently connected together by using a joint composed of a tubular part having the same inside diameter as the inner tubular member of the multi-walled pipe and a flange provided at one end of the tubular part concentrically therewith and having the same outside diameter as the multi-walled pipe, and in addition the hollow portion of the thermoplastic multi-walled pipe is kept sealed by the action of the flange.