Provided is a nucleating agent masterbatch for polyolefin resin excellent in dispersibility into a polyolefin resin, which nucleating agent masterbatch is capable of improving transparency and mechanical strength of the polyolefin resin, which is a crystalline polymer, which nucleating agent masterbatch is further excellent in resistance to heat coloring; and a polyolefin resin composition using the masterbatch. Specifically, provided is a nucleating agent masterbatch for polyolefin resin, wherein, based on 100 parts by mass of a fully hydrogenated petroleum resin (A) having a softening point of not lower than 100° C., 3 to 150 parts by mass of an aromatic phosphate metal salt (B) represented by the following general formula (1):