It is possible to improve the gel shape stability of the absorber and to provide an absorbent resin with excellent absorption performance. The water absorbent resin of this invention is a polymer of water-soluble ethylenically unsaturated monomer, and has the characteristics of following (1) and (2). (1) The collapse amount at the time of 20 times swelling is 30 mass% or less. (2) The dissolved amount in physiological saline is 25 mass% or less. (Measuring Method of Disintegration Amount at 20-Time Swelling) 5 g of an absorbent resin is added to 100 g of physiological saline to absorb physiological saline into the absorbent resin to obtain a gel. The obtained gel is divided into approximately equal five parts and put into a cylindrical mold having a length of 3.6 cm and a radius of 2.8 cm, respectively. The mass of the five cylindrical gels formed is measured and sampled with three gels except the heaviest and lightest. After measuring the mass Wa (g) of each sample, put the sample with the mass measured in the best sieve in the order of the sieve of 5.6mm of sieve size of JIS standard sieve and the base plate, and the low-tap shaker (rotation speed 290rpm, impact A mass of 165 rpm was shaken for 10 minutes and the mass Wb (g) passed under the sieve was measured. The amount of collapse of the sample is calculated by the following equation. Disintegration amount (%) of sample = Wb (g) / Wa (g) x 100 The average value of the disintegration amount with respect to three samples made into the measurement object is made into the disintegration amount at the time of 20 times swelling of a water absorbing resin.흡수체의 겔 형상 안정성을 향상시킬 수 있으며 뛰어난 흡수 성능을 갖춘 흡수성 수지를 제공한다. 본 발명의 흡수성 수지는 수용성 에틸렌성 불포화 단량체의 중합체로서, 하기 (1) 및 (2)의 특성을 구비한다. (1) 20배 팽윤시의 붕괴량이 30질량% 이하이다. (2) 생리식염수에 대한 용해량이 25질량% 이하이다. (20배 팽윤시의 붕괴량의 측정 방법) 생리식염수 100g 중에 흡수성 수지 5g을 넣고 흡수성 수지에 생리식염수를 흡수시켜서 겔을 얻는다. 얻어진 겔을 대략 균등하게 5분할하고, 각각 길이 3.6cm, 반경 2.8cm의 원통형의 틀에 넣어 성형한다. 성형된 5개의 원통형 겔의 질량을 측정하고 가장 무거운 것과 가장 가벼운 것을 제외한 3개
