PURPOSE: To enhance a crosslinked polyolefin pipe in adhesiveness by forming on the inner layer of the pipe a skin layer of crosslinked adhesive polymer equipped with polar groups which can enhance adhesiveness.

CONSTITUTION: On the inner layer of a crosslinked polyolefin pipe, a skin of a crosslinked adhesive polymer equipped with polar groups which can enhance adhesiveness, for example polyethylene or polypropylene with some free carbonic acid introduced thereinto or grafted with 0.1-10% maleic acid, is formed by simultaneous extrusion or the like. The adhesive polymer skin layer may be approximately 1mm- to 10μm-thick for being effective but should preferably be in the range of 50-500μms. The crosslinking method for the adhesive polymer may be electron beam crosslinking, silane water crosslinking, peroxide crosslinking, etc. As the result, joining by means of metal or resin joining pieces may be perfectly accomplished with more ease.