Water-absorbent resin particles comprising: a crosslinking polymer comprising a structural unit derived from an ethylenically unsaturated monomer, as polymer particles, wherein the ethylenically unsaturated monomer comprises at least one compound selected from the group consisting of (meth)acrylic acid and a salt thereof, a ratio of the (meth)acrylic acid and the salt thereof is 70 to 100 mol% with respect to a total amount of monomers for obtaining the water-absorbent resin particles, a water retention amount of physiological saline is 30 to 80 g/g when determined according to the method of the detailed description, a water absorption rate of physiological saline is 60 seconds or less when determined according to the method of the detailed description, a medium particle diameter is 300 to 700 μm wherein the medium particle diameter is determined by classification of the particles by sieving, calculating the mass percentage with respect to the total amount to obtain a particle size distribution and determining the cumulative mass percentage of 50% by mass, and a swelling height measured by the following procedures to is 7.0 to 9.2 mm, a container having a recess having a bottom area of 50 cm 2 is disposed in a state where the recess is open in a vertical direction, 1.00 g of water-absorbent resin particles are disposed in the recess, a non-woven fabric is disposed on the water-absorbent resin particles in the recess, a weight having a mass of 90 g is disposed on the non-woven fabric, physiological saline is supplied into the recess, a movement distance in a vertical direction of the weight when 300 seconds have passed from the start of swelling of the water-absorbent resin particles is measured as the swelling height, wherein the polymer particles are obtainable by using an internal crosslinking agent at the time of polymerizing the monomer, and using an external crosslinking agent after polymerization of the monomer, wherein the ratio of the external crosslinking agent with respect to the internal crosslinking agent is 5 to 100. a crosslinking polymer comprising a structural unit derived from an ethylenically unsaturated monomer, as polymer particles, wherein the ethylenically unsaturated monomer comprises at least one compound selected from the group consisting of (meth)acrylic acid and a salt thereof, a ratio of the (meth)acrylic acid and the salt thereof is 70 to 100 mol% with respect to a total amount of monomers for obtaining the water-absorbent resin particles, a water retention amount of physiological saline is 30 to 80 g/g when determined according to the method of the detailed description, a water absorption rate of physiological saline is 60 seconds or less when determined according to the method of the detailed description, a medium particle diameter is 300 to 700 μm wherein the medium particle diameter is determined by classification of the particles by sieving, calculating the mass percentage with respect to the total amount to obtain a particle size distribution and determining the cumulative mass percentage of 50% by mass, and a swelling height measured by the following procedures to is 7.0 to 9.2 mm, a container having a recess having a bottom area of 50 cm 2 is disposed in a state where the recess is open in a vertical direction, 1.00 g of water-absorbent resin particles are disposed in the recess, a non-woven fabric is disposed on the water-absorbent resin particles in the recess, a weight having a mass of 90 g is disposed on the non-woven fabric, physiological saline is supplied into the recess, a movement distance in a vertical direction of the weight when 300 seconds have passed from the start of swelling of the water-absorbent resin particles is measured as the swelling height, wherein the polymer particles are obtainable by using an internal crosslinking agent at the time of polymerizing the monomer, and using an external crosslinking agent after polymerization of the monomer, wherein the ratio of the external crosslinking agent with respect to the internal crosslinking agent is 5 to 100. a container having a recess having a bottom area of 50 cm 2 is disposed in a state where the recess is open in a vertical direction, 1.00 g of water-absorbent resin particles are disposed in the recess, a non-woven fabric is disposed on the water-absorbent resin particles in the recess, a weight having a mass of 90 g is disposed on the non-woven fabric, physiological saline is supplied into the recess, a movement distance in a vertical direction of the weight when 300 seconds have passed from the start of swelling of the water-absorbent resin particles is measured as the swelling height, wherein the polymer particles are obtainable by using an internal crosslinking agent at the time of polymerizing the monomer, and using an external crosslinking agent after polymerization of the monomer, wherein the ratio of the external crosslinking agent with respect to the internal crosslinking agent is 5 to 100.