A binder composition for secondary batteries comprising a composite latex comprising conjugated diene latex particles and acrylic copolymer latex particles, each present in an independent phase, wherein the composite latex has a pH of 7 or less; wherein the conjugated diene latex particles comprise a polymer of the following monomers: (a) a conjugated diene monomer which is present in an amount of 10 to 97.4% by weight, (b) a vinyl monomer which is present in an amount of 1 to 70% by weight, (c) an unsaturated carboxylic acid monomer which is present in an amount of 1 to 20% by weight, and (d) a hydroxyl group-containing monomer which is present in an amount of 0.5 to 5% by weight, based on the total weight of the conjugated diene latex particles; wherein the conjugated diene monomer is selected from the group consisting of 1,3-butadiene, isoprene and chloroprene; wherein the vinyl monomer comprises one or more monomers selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene and divinylbenzene; wherein the unsaturated carboxylic acid monomer comprises one or more monomers selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid; wherein the hydroxyl group-containing monomer comprises one or more monomers selected from the group consisting of hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxy butyl methacrylate; wherein the acrylic copolymer latex particles comprise a polymer of the following monomers: (a) a (meth)acrylic acid ester monomer which is present in an amount of 10 to 96.9% by weight, (b) a vinyl monomer which is present in an amount of 1 to 60% by weight, (c) an unsaturated carboxylic acid monomer which is present in an amount of 1 to 10% by weight, and (d) a hydroxyl group-containing monomer which is present in an amount of 1 to 10% by weight, based on the total weight of the acrylic copolymer latex particles; wherein the (meth)acrylic acid ester monomer comprises one or more monomers selected from the group consisting of methylacrylate, ethylacrylate, propylacrylate, isopropylacrylate, n-butylacrylate, isobutylacrylate, n-amylacrylate, isoamylacrylate, n-ethylhexylacrylate, 2-ethylhexylacrylate, methylmethacrylate, ethylmethacrylate, propylmethacrylate, isopropylmethacrylate, n-butylmethacrylate, isobutylmethacrylate, n-amyl methacrylate, isoamylmethacrylate, n-hexylmethacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate lauryl acrylate, ceryl acrylate, stearyl acrylate, lauryl methacrylate, cetyl methacrylate, and stearyl methacrylate; wherein the vinyl monomer comprises one or more monomers selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene and divinylbenzene; wherein the unsaturated carboxylic acid monomer comprises one or more monomers selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid; and wherein the hydroxyl group-containing monomer comprises one or more monomers selected from the group consisting of hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxy butyl methacrylate. (a) a conjugated diene monomer which is present in an amount of 10 to 97.4% by weight, (b) a vinyl monomer which is present in an amount of 1 to 70% by weight, (c) an unsaturated carboxylic acid monomer which is present in an amount of 1 to 20% by weight, and (d) a hydroxyl group-containing monomer which is present in an amount of 0.5 to 5% by weight, (a) a (meth)acrylic acid ester monomer which is present in an amount of 10 to 96.9% by weight, (b) a vinyl monomer which is present in an amount of 1 to 60% by weight, (c) an unsaturated carboxylic acid monomer which is present in an amount of 1 to 10% by weight, and (d) a hydroxyl group-containing monomer which is present in an amount of 1 to 10% by weight,