Provided is a water-absorbing agent that causes no or little fluctuation of feed rate when fed with use of a feeder. A water-absorbing agent containing a water-absorbing resin as a main component, the water-absorbing agent satisfying the following (a) and (b): (a) K-index is 70 or more； and (b) Moisture absorption blocking ratio, after 30 minutes of standing at a temperature of 25°C and a relative humidity of 80%RH, is 70 weight% or less, the K-index being defined by the following equation: K-index = 100 - (-438 + 3.6 x angle of repose + 3.5 x angle of difference + 7.9 x compressibility rate + 290 x bulk density (EDANA method)).
