A water-absorbing resin comprising a repeating unit derived from a water soluble unsaturated monomer having a dissociable group as a main component of a repeating unit of a main chain, wherein the water-absorbing resin has an internal crosslinked structure, wherein said water-absorbing resin is obtainable by a method comprising: a reaction step for reacting a first star-shaped polymer comprising the repeating unit derived from the water soluble unsaturated monomer as a main component of a repeating unit of each branched chain and having a first reactive functional group at a terminal of each branched chain with a second star-shaped polymer comprising the repeating unit derived from the water soluble unsaturated monomer as a main component of a repeating unit of each branched chain and having a second reactive functional group capable of forming a chemical bond with the first reactive functional group by reacting with each other at a terminal of each branched chain, a crosslinked structure index expressed by the following numerical formula 1 is 14 or more, a weight average molecular weight (Mw) of the water-absorbing resin after a hydrolysis treatment is 220, 000 or less, and a molecular weight distribution (Mw/Mn) of the water-absorbing resin after a hydrolysis treatment is 1.00 or more and 3.40 or less: Math. 1 Crosslinked structure index = Equilibrium swelling capacity with respect to 0.9 wt % physiological saline solution 1 / 3 / Weight average molecular weight Mw after hydrolysis treatment × 1000000 where the hydrolysis treatment is a treatment to leave 50 mg of the water-absorbing resin as a solids content to stand still in 10 g of a 0.1 mol/l aqueous sodium hydroxide solution for 3 weeks at 80°C, and the weight average molecular weight (Mw) is a value measured after the treatment. a reaction step for reacting a first star-shaped polymer comprising the repeating unit derived from the water soluble unsaturated monomer as a main component of a repeating unit of each branched chain and having a first reactive functional group at a terminal of each branched chain with a second star-shaped polymer comprising the repeating unit derived from the water soluble unsaturated monomer as a main component of a repeating unit of each branched chain and having a second reactive functional group capable of forming a chemical bond with the first reactive functional group by reacting with each other at a terminal of each branched chain, a crosslinked structure index expressed by the following numerical formula 1 is 14 or more, a weight average molecular weight (Mw) of the water-absorbing resin after a hydrolysis treatment is 220, 000 or less, and a molecular weight distribution (Mw/Mn) of the water-absorbing resin after a hydrolysis treatment is 1.00 or more and 3.40 or less: Math. 1 Crosslinked structure index = Equilibrium swelling capacity with respect to 0.9 wt % physiological saline solution 1 / 3 / Weight average molecular weight Mw after hydrolysis treatment × 1000000 where the hydrolysis treatment is a treatment to leave 50 mg of the water-absorbing resin as a solids content to stand still in 10 g of a 0.1 mol/l aqueous sodium hydroxide solution for 3 weeks at 80°C, and the weight average molecular weight (Mw) is a value measured after the treatment.