A method for preparing a superabsorbent polymer comprising the steps of: A) introducing an oxygen-containing gas into an aqueous monomer mixture comprising water soluble ethylenically unsaturated monomers having acid groups of which at least a part are neutralized, a crosslinking agent, and a polymerization inhibitor that inhibits polymerization of the water soluble ethylenically unsaturated monomers in the presence of oxygen, wherein the step A) is progressed such that a dissolved oxygen rate represented by Mathematical Formula 1 is greater than 1.0 and equal to or less than 2.5: DO 2 /DO 1 wherein, in Mathematical Formula 1, DO1 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately before introducing an oxygen-containing gas into the aqueous monomer mixture, and DO2 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after introducing an oxygen-containing gas into the aqueous monomer mixture; B) transferring the aqueous monomer mixture into which the oxygen-containing gas is introduced to a polymerization reactor; wherein the aqueous monomer mixture is transferred and introduced into the polymerization reactor at a temperature of 40°C to 90°C C) removing the oxygen from the aqueous monomer mixture immediately before the aqueous monomer mixture into which the oxygen-containing gas is introduced is introduced into the polymerization reactor, wherein the step C) is progressed such that a dissolved oxygen rate represented by the following Mathematical Formula 2 is 0.01 to 0.5: DO 3 /DO 2 wherein, in the Mathematical Formula 2, DO2 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after introducing an oxygen-containing gas into the aqueous monomer mixture, and DO3 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after removing oxygen from the aqueous monomer mixture; and D) progressing crosslinking polymerization of the water soluble ethylenically unsaturated monomers in the polymerization reactor, to form a hydrogel polymer comprising a first crosslinked polymer. A) introducing an oxygen-containing gas into an aqueous monomer mixture comprising water soluble ethylenically unsaturated monomers having acid groups of which at least a part are neutralized, a crosslinking agent, and a polymerization inhibitor that inhibits polymerization of the water soluble ethylenically unsaturated monomers in the presence of oxygen, wherein the step A) is progressed such that a dissolved oxygen rate represented by Mathematical Formula 1 is greater than 1.0 and equal to or less than 2.5: DO 2 /DO 1 wherein, in Mathematical Formula 1, DO1 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately before introducing an oxygen-containing gas into the aqueous monomer mixture, and DO2 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after introducing an oxygen-containing gas into the aqueous monomer mixture; wherein the step A) is progressed such that a dissolved oxygen rate represented by Mathematical Formula 1 is greater than 1.0 and equal to or less than 2.5: DO 2 /DO 1 wherein, in Mathematical Formula 1, DO1 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately before introducing an oxygen-containing gas into the aqueous monomer mixture, and DO2 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after introducing an oxygen-containing gas into the aqueous monomer mixture; B) transferring the aqueous monomer mixture into which the oxygen-containing gas is introduced to a polymerization reactor; wherein the aqueous monomer mixture is transferred and introduced into the polymerization reactor at a temperature of 40°C to 90°C C) removing the oxygen from the aqueous monomer mixture immediately before the aqueous monomer mixture into which the oxygen-containing gas is introduced is introduced into the polymerization reactor, wherein the step C) is progressed such that a dissolved oxygen rate represented by the following Mathematical Formula 2 is 0.01 to 0.5: DO 3 /DO 2 wherein, in the Mathematical Formula 2, DO2 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after introducing an oxygen-containing gas into the aqueous monomer mixture, and DO3 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after removing oxygen from the aqueous monomer mixture; and wherein the step C) is progressed such that a dissolved oxygen rate represented by the following Mathematical Formula 2 is 0.01 to 0.5: DO 3 /DO 2 wherein, in the Mathematical Formula 2, DO2 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after introducing an oxygen-containing gas into the aqueous monomer mixture, and DO3 is the amount of dissolved oxygen (mg/L) in the aqueous monomer mixture, measured immediately after removing oxygen from the aqueous monomer mixture; and D) progressing crosslinking polymerization of the water soluble ethylenically unsaturated monomers in the polymerization reactor, to form a hydrogel polymer comprising a first crosslinked polymer.