A production method for producing a resin additive composition, the method being a method for handling, as a solid, a compound that can maintain a liquid state or fluid state at 100°C for 30 minutes or longer, the method comprising mixing 100 parts by mass of a styrene-based elastomer with 50 to 250 parts by mass of a compound that can maintain a liquid state or fluid state at 100°C for 30 minutes or longer, wherein the compound is a resin additive having a melting point of 100°C or lower; and wherein the compound is a compound represented by Formula: where A 1 represents -O-(CH 2 CH 2) a -, -(OCH 2 CH 2) a -, -(CH 2 CH 2) a -O-,-(CH 2 CH 2 O) a -, -CH 2 CH 2 -(C=O)-, -O-(C=O)-, -(C=O)-O-, -O-(C=O)-O-, -NH-,-NH-(CH 2 CH 2) a -, -NH-CH 2 CH 2 -(C=O)-O-, or a combination thereof, a represents an integer between 1 and 100, and j represents an integer between 1 to 4, when j is 1, X 1 represents a hydrogen atom, a hydroxy group, a branched or linear alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or a group represented by Formula or Formula, and R 1 represents a group represented by Formula, when j is 2, X 1 represents an alkylidene group having 1 to 40 carbon atoms, and R 1 represents a branched or linear alkyl group having 1 to 40 carbon atoms or a group represented by Formula, and at least one R 1 represents a group represented by Formula, when j is 3, X 1 represents an alkanetriyl group having 1 to 40 carbon atoms, and R 1 represents a branched or linear alkyl group having 1 to 40 carbon atoms or a group represented by Formula, and at least one R 1 represents a group represented by Formula, and when j is 4, X 1 represents an alkanetetrayl group having 1 to 40 carbon atoms, and R 1 represents a branched or linear alkyl group having 1 to 40 carbon atoms or a group represented by Formula, and at least one R 1 represents a group represented by Formula excluding a compound having a peroxide structure; where R 2 represents a hydrogen atom, a hydroxy group, a branched or linear alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, a hydroxyalkoxy group having 1 to 30 carbon atoms, or an oxy-radical; and where R 3 represents any of the atoms or groups represented by R2 in Formula; or wherein the compound is a compound represented by Formula: where R 4 represents a hydrogen atom, a hydroxy group, a branched or linear alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, a hydroxyalkoxy group having 1 to 30 carbon atoms, or an oxy-radical, and R 5 represents a branched or linear alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or a group represented by Formula; and where R 2 represents a hydrogen atom, a hydroxy group, a branched or linear alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, a hydroxyalkoxy group having 1 to 30 carbon atoms, or an oxy-radical, or wherein the compound is an NO-alkyl type hindered amine compound having a triazine structure or a spiroglycol structure.