A method of producing an acid-resistant nanomembrane with an improved flow rate, the method comprising: immersing a porous support in a first solution, wherein the first solution contains a first amine-based compound represented by Chemical Formula 1, a second amine-based compound, a phenol-based compound, and a hydrophilic polymer; forming a polyamide layer on the surface of the immersed porous support by treating the porous support with a second solution containing an acid halide compound; and subjecting the porous support, on which the polyamide layer has been formed, to hydrophilization with a hydrophilization solution: (in Chemical Formula 1, R 1 and R 2 are each independently a C 1 -C 10 alkylene group, and n is an integer of 1 to 100); wherein the first solution contains the first amine-based compound and the second amine-based compound in a weight ratio of 1:0.04 to 2, and contains the first amine-based compound and the phenol-based compound in a weight ratio of 1:0.02 to 1; wherein the hydrophilic polymer in the first solution comprises one or more selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol in an amount of 1 part by weight to 35 parts by weight based on 100 parts by weight of the first amine-based compound; wherein the second amine-based compound comprises one or more selected from the group consisting of m-phenylenediamine and piperazine; wherein the phenol-based compound comprises one or more selected from the group consisting of pyrocatechol, resorcinol, pyrogallol, and phloroglucinol; wherein the hydrophilization solution comprises one or more selected from the group consisting of potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide, sulfuric acid, sodium sulfate, sodium sulfite, and sodium hydrogen carbonate; and the hydrophilization solution has a concentration of 0.0 wt% to 2 wt%. immersing a porous support in a first solution, wherein the first solution contains a first amine-based compound represented by Chemical Formula 1, a second amine-based compound, a phenol-based compound, and a hydrophilic polymer; forming a polyamide layer on the surface of the immersed porous support by treating the porous support with a second solution containing an acid halide compound; and subjecting the porous support, on which the polyamide layer has been formed, to hydrophilization with a hydrophilization solution: (in Chemical Formula 1, R 1 and R 2 are each independently a C 1 -C 10 alkylene group, and n is an integer of 1 to 100); wherein the first solution contains the first amine-based compound and the second amine-based compound in a weight ratio of 1:0.04 to 2, and contains the first amine-based compound and the phenol-based compound in a weight ratio of 1:0.02 to 1; wherein the hydrophilic polymer in the first solution comprises one or more selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol in an amount of 1 part by weight to 35 parts by weight based on 100 parts by weight of the first amine-based compound; wherein the second amine-based compound comprises one or more selected from the group consisting of m-phenylenediamine and piperazine; wherein the phenol-based compound comprises one or more selected from the group consisting of pyrocatechol, resorcinol, pyrogallol, and phloroglucinol; wherein the hydrophilization solution comprises one or more selected from the group consisting of potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide, sulfuric acid, sodium sulfate, sodium sulfite, and sodium hydrogen carbonate; and the hydrophilization solution has a concentration of 0.0 wt% to 2 wt%.