Production method for water-absorbing resin

A production method for a water-absorbing resin comprising:

• a polymerization step for polymerizing an aqueous solution of an unsaturated monomer to obtain a hydrogel polymer;
• a drying step for drying the hydrogel polymer to obtain a particulate water-absorbing resin;
• and
• a surface cross-linking step for surface cross-linking the particulate water-absorbing resin;
• wherein comprised is a pneumatic transportation step for pneumatic transporting a water-absorbing resin powder substance generated in at least one step selected from the drying step, a pulverization step, a classification step, the surface cross-linking step, a cooling step, a granule sizing step, and a fine powder capturing step, in a pipeline with a surface roughness (Rz) of the inner surface of equal to or smaller than 800 nm, by using gas with a dew point of −5° C. to −100° C.