A method for producing an aqueous liquid containing a vinyl polymer, which comprises filling a closed container having a gas outlet with a mixed liquid containing water and a hydrophilic organic solvent with a boiling point of lower than 100°C, wherein the amount of water in the mixed liquid to be filled in the closed container is at least 50 mass%, per the total amount of water and the hydrophilic organic solvent, wherein a vinyl polymer having hydrophobic groups and hydrophilic groups is dissolved or dispersed, to form a liquid phase and a gas phase, then forming a part of the liquid of the liquid phase into small droplets which are liquid droplets having a particle size of at most 1,000 μm and bringing the small droplets into contact with the gas phase to vaporize the hydrophilic organic solvent in the small droplets and removing the gas of the gas phase containing the vaporized hydrophilic organic solvent from the gas outlet of the closed container, whereby the amount of the hydrophilic organic solvent in the liquid phase is reduced to at most 1 mass% per the total amount of the hydrophilic organic solvent and water, wherein the hydrophilic groups are acidic groups or basic groups, or the hydrophilic groups are neutralized acidic groups or neutralized basic groups, wherein the vinyl polymer is a polymer having units derived from a monomer (a) having a hydrophobic group and units derived from a monomer (b) having a basic group or an acidic group, or a derivative of the polymer, wherein said derivative is a polymer having neutralized acidic groups or neutralized basic groups which is obtained by neutralizing acidic groups or basic groups of the polymer, wherein the closed container has a circulating system to take out a part of the liquid of the liquid phase and control the temperature of the taken out liquid to form it into small droplets and to discharge them in the gas phase, and wherein the closed container has a liquid outlet to discharge the liquid of the liquid phase and a liquid inlet to introduce the liquid to the gas phase, the circulating system is an external circulating system formed between the liquid outlet and the liquid inlet, and the external circulating system has a means to control the temperature and the pressure of the liquid flowing therein. wherein the hydrophilic groups are acidic groups or basic groups, or the hydrophilic groups are neutralized acidic groups or neutralized basic groups, wherein the vinyl polymer is a polymer having units derived from a monomer (a) having a hydrophobic group and units derived from a monomer (b) having a basic group or an acidic group, or a derivative of the polymer, wherein said derivative is a polymer having neutralized acidic groups or neutralized basic groups which is obtained by neutralizing acidic groups or basic groups of the polymer, wherein the closed container has a circulating system to take out a part of the liquid of the liquid phase and control the temperature of the taken out liquid to form it into small droplets and to discharge them in the gas phase, and wherein the closed container has a liquid outlet to discharge the liquid of the liquid phase and a liquid inlet to introduce the liquid to the gas phase, the circulating system is an external circulating system formed between the liquid outlet and the liquid inlet, and the external circulating system has a means to control the temperature and the pressure of the liquid flowing therein.