According to the present invention, there is provided a modified polyolefin resin having the following merits:(1) The amount of bound unsaturated carboxylic acid, a derivative thereof or unsaturated epoxy compound is high.(2) The change of the melt flow rate during the modification is small.(3) The physical properties are of high grade.(4) The transparency is improved due to the graft of unsaturated aromatic compound.The modified polyolefin resin of the present invention can be used for adhesives, covering materials, binders, laminate bonding agent and polymer alloy constituents.