To provide a method for producing a water absorbing polymer obtained by using a polysaccharide and exhibiting a high water absorbing property.

The method for producing the water absorbing polymer includes a step of obtaining modified cellulose by reacting cellulose with an etherifying agent and/or an esterifying agent in the presence of an ionic liquid. Preferably, the method further includes a step of obtaining crosslinked cellulose by reacting the modified cellulose with a crosslinking agent. Absorptive resin particles containing a water absorbing polymer obtained by the method and crosslinked polyacrylic acid (polyacrylate) are also provided. Contents of the water absorbing polymer and the crosslinked polyacrylic acid (polyacrylate) are preferably 15-95 wt.% and 5-85 wt.%, respectively, based on a total weight of the water absorbing polymer and the crosslinked polyacrylic acid (polyacrylate).