A method of coating a surface of an aluminum fin material with a hydrophilic film, that is a method of treating a surface of an aluminum heat exchanger, wherein, bringing a chemical conversion treatment agent into contact with a surface of an aluminum fin material used for the aluminum heat exchanger to form a chemical conversion film; and bringing a hydrophilization treatment agent into contact with thus obtained chemical conversion film to form a hydrophilic film, wherein, the hydrophilization treatment agent comprises: a (meth)acrylic resin including a repeating unit derived from an acrylic acid monomer and/or a repeating unit derived from a methacrylic acid monomer; polyvinyl alcohol; a polyalkylene ether resin; and crosslinking microparticles,wherein, the (meth)acrylic resin: does not comprise a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group; has a weight average molecular weight of from 20,000 to 2,000,000; and has an acid value of the solid component of the resin of from 100 to 800 mgKOH/g, wherein, the polyalkylene ether resin has a weight average molecular weight of from 5,000 to 500,000, the crosslinking microparticles are obtained by copolymerizing from 30 to 95 mass% of a monomer (a) represented by the following formula, from 5 to 60 mass% of a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, and from 0 to 50 mass% of another polymerizable monomer (c), wherein, R 1 represents a hydrogen atom or a methyl group, and R 2 represents CH 2 or C 2 H 4 characterised in that a content rate of a solid component of the (meth)acrylic resin is from 10 to 30 mass%, a content rate of a solid component of the polyvinyl alcohol is from 5 to 40 mass%, a content rate of a solid component of the polyalkylene ether resin is from 40 to 50 mass%, and a content rate of a solid component of the crosslinking microparticles is from 10 to 20 mass%, in the total solid component of the hydrophylization treatment agent, a ratio of the content of the polyvinyl alcohol to the content of the polyalkylene ether resin, wherein the content of the polyvinyl alcohol /content of the polyalkylene ether resin) is from 1/9 to 1/1. a (meth)acrylic resin including a repeating unit derived from an acrylic acid monomer and/or a repeating unit derived from a methacrylic acid monomer; polyvinyl alcohol; a polyalkylene ether resin; and crosslinking microparticles,wherein, the (meth)acrylic resin: does not comprise a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group; has a weight average molecular weight of from 20,000 to 2,000,000; and has an acid value of the solid component of the resin of from 100 to 800 mgKOH/g, wherein, does not comprise a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group; has a weight average molecular weight of from 20,000 to 2,000,000; and has an acid value of the solid component of the resin of from 100 to 800 mgKOH/g, wherein, the polyalkylene ether resin has a weight average molecular weight of from 5,000 to 500,000, the crosslinking microparticles are obtained by copolymerizing from 30 to 95 mass% of a monomer (a) represented by the following formula, from 5 to 60 mass% of a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, and from 0 to 50 mass% of another polymerizable monomer (c), wherein, R 1 represents a hydrogen atom or a methyl group, and R 2 represents CH 2 or C 2 H 4 characterised in that wherein, R 1 represents a hydrogen atom or a methyl group, and R 2 represents CH 2 or C 2 H 4 characterised in that a content rate of a solid component of the (meth)acrylic resin is from 10 to 30 mass%, a content rate of a solid component of the polyvinyl alcohol is from 5 to 40 mass%, a content rate of a solid component of the polyalkylene ether resin is from 40 to 50 mass%, and a content rate of a solid component of the crosslinking microparticles is from 10 to 20 mass%, in the total solid component of the hydrophylization treatment agent, a ratio of the content of the polyvinyl alcohol to the content of the polyalkylene ether resin, wherein the content of the polyvinyl alcohol /content of the polyalkylene ether resin) is from 1/9 to 1/1.