Abstract: Provided are: a nucleating agent capable of imparting excellent mechanical properties to a molded article; a resin composition; a method of producing a resin composition; and a molded article. The nucleating agent contains: (A) an aromatic phosphate metal salt having a structure represented by Formula (1) (wherein, R1 to R5 each independently represent a hydrogen atom or an alkyl group; n represents 1 or 2; when n is 1, M1 represents an alkali metal or dihydroxyaluminum; and when n is 2, M1 represents an alkaline earth metal, zinc, or hydroxyaluminum); and (B) a carboxylic acid metal salt having a structure represented by Formula (2) (wherein, M2 represents an alkali metal, an alkaline earth metal, hydroxyaluminum, or dihydroxyaluminum; a represents 1 or 2; x represents 1 or 2; a and x satisfy ax=2; and Z represents a group having a structure represented by Formula (3) or (4)).

Abstract: Provided are: a nucleating agent for a polyolefin resin having an excellent ? crystal-forming effect; a nucleating agent composition for a polyolefin resin containing the nucleating agent; a polyolefin resin masterbatch; a polyolefin resin composition; a molded article of the composition; a film of the composition; a method of producing a porous film; and a package. The nucleating agent contains a compound represented by Formula (1) below wherein M represents a monovalent to trivalent metal atom having a specific gravity of 4.