It is an object to provide a new polyolefin hybrid polymer composed of a polyolefin segment and a polar polymer segment (Z) and a method for manufacturing the hybrid polymer by an industrially advantageous procedure. A polyolefin hybrid polymer composed of a polyolefin segment and a polar polymer segment (Z), wherein the polyolefin hybrid polymer is a modified compound of maleic polyolefin (A), is characterized by comprising a constitutional unit represented by the general formula (I): ##STR00001## wherein Z represents a polar polymer segment obtained by polymerizing monomers of at least one kind selected from organic compounds having at least one carbon-carbon unsaturated bond, and F represents a group including an unsaturated bond.