A process for producing a water-absorbing resin powder, comprising, in this order, the steps of: a first classification step of classifying a water-absorbing resin powder, a surface-crosslinking step of surface-crosslinking the water-absorbing resin powder after the first classification step, a water addition step of adding 0.01 to 50 parts by weight of a water-based liquid relative to 100 parts by weight of the water-absorbing resin powder in at least one stage of after the surface-crosslinking step, during the surface-crosslinking step, and before the surface-crosslinking step, a second classification step of classifying the water-absorbing resin powder after the surface-crosslinking step and the water addition step, wherein an apparatus for classifying the water-absorbing resin powder in the second classification step is joined to a lower part of an apparatus for adding water in the water addition step, a conveying step of conveying the water-absorbing resin powder after the second classification step using a mechanical conveying apparatus selected from the group consisting of a screw feeder, a belt conveyor, a bucket conveyor, a flight conveyor, a vibration feeder and an air conveying device, and optionally a third classification step of classifying the water-absorbing resin powder after the conveying step for controlling the particle size distribution of the water-absorbing resin powder by classification with a sieve, wherein: the moisture content of the water-absorbing resin powder before the second classification step is 0.2 wt.% or more, as determined in accordance with EDANA ERT 430.2-2, agglomerates of the water-absorbing resin powder with a particle diameter 10 mm or larger, left on a sieve with meshes of 10 mm, are removed in the second classification step after obtaining water-absorbing resin particles with a particle diameter smaller than 1 mm in the first classification step, and the production amount per line of the water-absorbing resin powder is 300 kg/hr or more. a first classification step of classifying a water-absorbing resin powder, a surface-crosslinking step of surface-crosslinking the water-absorbing resin powder after the first classification step, a water addition step of adding 0.01 to 50 parts by weight of a water-based liquid relative to 100 parts by weight of the water-absorbing resin powder in at least one stage of after the surface-crosslinking step, during the surface-crosslinking step, and before the surface-crosslinking step, a second classification step of classifying the water-absorbing resin powder after the surface-crosslinking step and the water addition step, wherein an apparatus for classifying the water-absorbing resin powder in the second classification step is joined to a lower part of an apparatus for adding water in the water addition step, a conveying step of conveying the water-absorbing resin powder after the second classification step using a mechanical conveying apparatus selected from the group consisting of a screw feeder, a belt conveyor, a bucket conveyor, a flight conveyor, a vibration feeder and an air conveying device, and optionally a third classification step of classifying the water-absorbing resin powder after the conveying step for controlling the particle size distribution of the water-absorbing resin powder by classification with a sieve, wherein: the moisture content of the water-absorbing resin powder before the second classification step is 0.2 wt.% or more, as determined in accordance with EDANA ERT 430.2-2, agglomerates of the water-absorbing resin powder with a particle diameter 10 mm or larger, left on a sieve with meshes of 10 mm, are removed in the second classification step after obtaining water-absorbing resin particles with a particle diameter smaller than 1 mm in the first classification step, and the production amount per line of the water-absorbing resin powder is 300 kg/hr or more. the moisture content of the water-absorbing resin powder before the second classification step is 0.2 wt.% or more, as determined in accordance with EDANA ERT 430.2-2, agglomerates of the water-absorbing resin powder with a particle diameter 10 mm or larger, left on a sieve with meshes of 10 mm, are removed in the second classification step after obtaining water-absorbing resin particles with a particle diameter smaller than 1 mm in the first classification step, and the production amount per line of the water-absorbing resin powder is 300 kg/hr or more.