Disclosed are a mixture of at least two amide-based compounds represented by General Formula (1): ##STR00001## wherein a represents an integer of 2 to 6, R.sup.1 represents a C.sub.2-30 saturated or unsaturated aliphatic polycarboxylic acid residue, and the aliphatic polycarboxylic acid has a valency of 2 to 6, and two to six R.sup.2 groups are the same or different, and each represent a trans-2-alkylcyclohexylamine residue or a cis-2-alkylcyclohexylamine residue, the mixture having a content of a trans-2-alkylcyclohexylamine residue of at least 70 mole % but less than 100 mole % of the total 2-alkylcyclohexylamine residues in the mixture, or an all-trans amide-based compound wherein all of the 2 to 6 R.sup.2 groups represent a trans-2-alkylcyclohexylamine residue; a polyolefin resin nucleating agent comprising the mixture or the all-trans amide-based compound; a polyolefin resin composition containing the amide-based compound or the mixture; a molded article obtainable by molding the composition.