PURPOSE: To obtain a novel adhesive suitable for the bonding or connection of (crosslinked) polyolefin (pipes), by compounding a polyolefin, an organic peroxide crosslinking agent, and a good solvent of said polyolefin.

CONSTITUTION: The objective adhesive is obtained by using (A) a polyolefin crosslinkable with an organic peroxide crosslinking agent, e.g. a low density linear polyethylene; an α-olefin polymer containing about 0.001W10wt% ethylenic unsaturated carboxylic acid (anhydride) as a copolymer component or a graft component (e.g. ethylene-maleic acid copolymer), an ehylene-vinyl acetate copolymer, an ethylene-propylene-diene copolymer, etc., (B) an organic peroxide (e.g. dicumyl peroxide) and (C) a good solvent of the component (A) (e.g. xylene, decaline, etc.). The compound (C) is heated at or above the melting point of the component (A), and the component (A) and an antioxidant, etc. are added and dissolved in the component (C) by stirring. A definite amount of the component (B) and a sulfur vulcanizing agent are added to the solution at or below the decomposition temperature of the component (B) to obtain the objective adhesive.