An object of the present invention is to provide a method for producing a water absorbing agent, whereby the ability to produce the water absorbing agent is enhanced or the amount of a residual surface crosslinking agent is reduced (or Anti-Caking property are enhanced) in the production of a water absorbing agent having high physical properties (particularly, high liquid permeability and Anti-Caking property), whereas the surface crosslinking step tends to be a rate-determining step in the current state of the art. In this method for producing a water absorbing agent, an additive selected from a polyvalent metal cation-containing compound, water-insoluble inorganic fine particles, and a cationic polymer compound is used, and surface crosslinking, particularly surface crosslinking with an alkylene carbonate compound, is performed under conditions where a temperature in a heat treatment system is controlled to be in a range from 100 °C to 300 °C, and a dew point in the heat treatment system is controlled to be lower than 45 °C.
