A method of preparing a superabsorbent polymer, comprising the steps of: forming a monomer composition including water-soluble ethylenic unsaturated monomers and a polymerization initiator, wherein the content of the water-soluble ethylenic unsaturated monomers in the monomer composition is 0.01 to 1.0 % by weight; polymerizing the monomer composition in a polymerization reactor so as to prepare a water-containing gel polymer; mixing the water-containing gel polymer and a base-treated fine powder regranulated body which are different from each other in degree of neutralization; drying and pulverizing a mixture of the water-containing gel polymer and the base-treated fine powder regranulated body; sorting the pulverized mixture so as to prepare a base resin; and surface-treating the base resin including the step of surface-crosslinking the base resin at a temperature of 150 to 300 °C for 20 to 90 min, wherein the base-treated fine powder regranulated body is obtained by drying, pulverizing, and sorting the water-containing gel polymer obtained from the polymerization process, and then treating the resulting fine powder polymer having a particle size of smaller than 150 μm with an alkaline solution, followed by regranulation, wherein the alkaline solution is one or more solutions selected from the group consisting of NaOH, Na 2 CO 3, and NaHCO 3 having a concentration of 1 to 10 % by weight, wherein the surface treating step of the base resin includes the step of surface-treating the base resin with a surface treatment solution including: a surface-crosslinking agent which is a diol or glycol-based compound having 2 to 8 carbon atoms; an alcohol or glycol-based compound having 3 or more carbon atoms and a boiling point of 90 °C or higher; and water, wherein the water-containing gel polymer has a degree of neutralization of 70 to 80 mol%, the base-treated fine powder regranulated body has a degree of neutralization of 71 to 100 mol%, and the water-containing gel polymer and the base-treated fine powder regranulated body are different from each other in the degree of neutralization, wherein the water-containing gel polymer and the base-treated fine powder regranulated body are mixed at a weight ratio of 95:5 to 70:30. forming a monomer composition including water-soluble ethylenic unsaturated monomers and a polymerization initiator, wherein the content of the water-soluble ethylenic unsaturated monomers in the monomer composition is 0.01 to 1.0 % by weight; polymerizing the monomer composition in a polymerization reactor so as to prepare a water-containing gel polymer; mixing the water-containing gel polymer and a base-treated fine powder regranulated body which are different from each other in degree of neutralization; drying and pulverizing a mixture of the water-containing gel polymer and the base-treated fine powder regranulated body; sorting the pulverized mixture so as to prepare a base resin; and surface-treating the base resin including the step of surface-crosslinking the base resin at a temperature of 150 to 300 °C for 20 to 90 min, wherein the base-treated fine powder regranulated body is obtained by drying, pulverizing, and sorting the water-containing gel polymer obtained from the polymerization process, and then treating the resulting fine powder polymer having a particle size of smaller than 150 μm with an alkaline solution, followed by regranulation, wherein the alkaline solution is one or more solutions selected from the group consisting of NaOH, Na 2 CO 3, and NaHCO 3 having a concentration of 1 to 10 % by weight, wherein the surface treating step of the base resin includes the step of surface-treating the base resin with a surface treatment solution including: a surface-crosslinking agent which is a diol or glycol-based compound having 2 to 8 carbon atoms; an alcohol or glycol-based compound having 3 or more carbon atoms and a boiling point of 90 °C or higher; and water, wherein the water-containing gel polymer has a degree of neutralization of 70 to 80 mol%, the base-treated fine powder regranulated body has a degree of neutralization of 71 to 100 mol%, and the water-containing gel polymer and the base-treated fine powder regranulated body are different from each other in the degree of neutralization, wherein the water-containing gel polymer and the base-treated fine powder regranulated body are mixed at a weight ratio of 95:5 to 70:30.