To obtain a composition in which the polyolefin obtained by using a metallocene catalyst is improved by mixing the polyolefin with a vinylidene fluoride in a specified ratio.

100 pts.wt. polyolefin obtained by using a metallocene catalyst is mixed with 0.05-5 pts.wt. vinylidene fluoride resin. The polyolefin obtained by using a metallocene is exemplified by a polyethylene or an ethylene/butene copolymer. The vinylidene fluoride resin is exemplified by a vinylidene fluoride/ hexafluoropropylene copolymer. When the vinylidene fluoride is used, and the mixture is extruded around a cable conductor, the change in resin pressure can be reduced, the change in the outside diameter of the extruded insulator and the formation of resinous deposit can be reduced, the formation of roughness of the external surface can be reduced, and the abnormality of appearance, etc., can be satisfactorily suppressed.