A binder comprising a polyvinyl alcohol-based polymer, wherein the polyvinyl alcohol-based polymer has an average saponification value of 85.0 mol% to 89.0 mol% as measured according to JIS K6726 and meets requirement: based on data obtained by measurement of the polyvinyl alcohol-based polymer by liquid chromatography, a value represented by formula shown below is 22 or more, wherein the measurement is performed with a liquid chromatography system equipped with a charged aerosol detector and a Thermo Scientific Acclaim TM 300 column, catalog number: 060266, carbon load: 8%, maximum pressure: 4500 psi, particle size: 3 μm, pore size: 300 Å, stationary phase: C18, surface area: 100 m 2 /g, length: 150 mm, diameter: 4.6 mm, pH: 2.5 to 7.5, material: glass lined tubing, under the measurement conditions described below, wherein the data represent a baseline-normalized intensity over a retention time of 5.0 to 12.0 minutes at a sampling interval of 500 ms, and wherein the value represented by formula is calculated from formulae and shown below, wherein the intensity at a retention time T i [min] is represented by P i [pA]. Measurement conditions - Concentration of an aqueous polyvinyl alcohol-based polymer solution: 0.1% by mass - Injection volume of the aqueous polyvinyl alcohol-based polymer solution: 2 μL - Column temperature: 50°C - Flow rate: 1.0 mL/min - Eluent: a mixed solvent of water and methanol - Eluent gradient conditions: the ratio of water and methanol in the eluent changes from 95:5 to 15:85 at a constant rate over a run time from minutes 0 to 10; and the ratio of water and methanol in the eluent is constant at 15:85 over a run time from minutes 10 to 15. Formulae T n = ∑ T i × P i / ∑ P i T w = ∑ T i 2 × P i / ∑ T i × P i T w / T n − 1 × 1000 wherein the measurement is performed with a liquid chromatography system equipped with a charged aerosol detector and a Thermo Scientific Acclaim TM 300 column, catalog number: 060266, carbon load: 8%, maximum pressure: 4500 psi, particle size: 3 μm, pore size: 300 Å, stationary phase: C18, surface area: 100 m 2 /g, length: 150 mm, diameter: 4.6 mm, pH: 2.5 to 7.5, material: glass lined tubing, under the measurement conditions described below, wherein the data represent a baseline-normalized intensity over a retention time of 5.0 to 12.0 minutes at a sampling interval of 500 ms, and wherein the value represented by formula is calculated from formulae and shown below, wherein the intensity at a retention time T i [min] is represented by P i [pA]. Measurement conditions - Concentration of an aqueous polyvinyl alcohol-based polymer solution: 0.1% by mass - Injection volume of the aqueous polyvinyl alcohol-based polymer solution: 2 μL - Column temperature: 50°C - Flow rate: 1.0 mL/min - Eluent: a mixed solvent of water and methanol - Eluent gradient conditions: the ratio of water and methanol in the eluent changes from 95:5 to 15:85 at a constant rate over a run time from minutes 0 to 10; and the ratio of water and methanol in the eluent is constant at 15:85 over a run time from minutes 10 to 15. Formulae T n = ∑ T i × P i / ∑ P i T w = ∑ T i 2 × P i / ∑ T i × P i T w / T n − 1 × 1000 Measurement conditions - Concentration of an aqueous polyvinyl alcohol-based polymer solution: 0.1% by mass - Injection volume of the aqueous polyvinyl alcohol-based polymer solution: 2 μL - Column temperature: 50°C - Flow rate: 1.0 mL/min - Eluent: a mixed solvent of water and methanol - Eluent gradient conditions: the ratio of water and methanol in the eluent changes from 95:5 to 15:85 at a constant rate over a run time from minutes 0 to 10; and the ratio of water and methanol in the eluent is constant at 15:85 over a run time from minutes 10 to 15. - Concentration of an aqueous polyvinyl alcohol-based polymer solution: 0.1% by mass - Injection volume of the aqueous polyvinyl alcohol-based polymer solution: 2 μL - Column temperature: 50°C - Flow rate: 1.0 mL/min - Eluent: a mixed solvent of water and methanol - Eluent gradient conditions: the ratio of water and methanol in the eluent changes from 95:5 to 15:85 at a constant rate over a run time from minutes 0 to 10; and the ratio of water and methanol in the eluent is constant at 15:85 over a run time from minutes 10 to 15. Formulae T n = ∑ T i × P i / ∑ P i T w = ∑ T i 2 × P i / ∑ T i × P i T w / T n − 1 × 1000