A method of producing a resin composition, obtained by reacting a tri-functional or more (meth)acrylate having an alkoxysilyl group; and at least one of a metal oxide fine particle having a hydroxyl group on a surface thereof and a metal alkoxide, characterized in that the method comprises: a first step of obtaining tri-functional or more (meth)acrylate having an alkoxysilyl group by copolymerizing a tri-functional or more (meth)acrylic monomer, or oligomer or polymer thereof and a monomer having an alkoxysilyl group using a polymerization initiator, refluxing the mixture at a predetermined temperature, wherein the monomer having the alkoxysilyl group is selected from the group consisting of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, p-styryltrimethoxysilane, 3-acryloxypropyltriethoxysilane and vinyltriacetoxysilane, and a blending molar ratio of the tri-functional or more (meth)acrylic monomer, or oligomer or polymer thereof and the monomer having an alkoxysilyl group is in the range of 55:45 to 99:1; and a second step of binding the tri-functional or more (meth)acrylate having the alkoxysilyl group obtained in the first step and at least one of a metal oxide fine particle having a hydroxyl group on a surface thereof and a metal alkoxide to obtain a target resin composition by a condensation reaction, in which a content of at least one of the metal oxide fine particle having a hydroxyl group on a surface thereof and the metal alkoxide is, relative to a mixed amount of the (meth)acrylic polymer having an alkoxysilyl group and at least one of the metal oxide fine particle having a hydroxyl group on a surface thereof and the metal alkoxide, is in the range of 1.0 to 70% by weight. a first step of obtaining tri-functional or more (meth)acrylate having an alkoxysilyl group by copolymerizing a tri-functional or more (meth)acrylic monomer, or oligomer or polymer thereof and a monomer having an alkoxysilyl group using a polymerization initiator, refluxing the mixture at a predetermined temperature, wherein the monomer having the alkoxysilyl group is selected from the group consisting of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, p-styryltrimethoxysilane, 3-acryloxypropyltriethoxysilane and vinyltriacetoxysilane, and a blending molar ratio of the tri-functional or more (meth)acrylic monomer, or oligomer or polymer thereof and the monomer having an alkoxysilyl group is in the range of 55:45 to 99:1; and a second step of binding the tri-functional or more (meth)acrylate having the alkoxysilyl group obtained in the first step and at least one of a metal oxide fine particle having a hydroxyl group on a surface thereof and a metal alkoxide to obtain a target resin composition by a condensation reaction, in which a content of at least one of the metal oxide fine particle having a hydroxyl group on a surface thereof and the metal alkoxide is, relative to a mixed amount of the (meth)acrylic polymer having an alkoxysilyl group and at least one of the metal oxide fine particle having a hydroxyl group on a surface thereof and the metal alkoxide, is in the range of 1.0 to 70% by weight.