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×angle of repose+3.5×angle of difference+7.9×compressibility rate+290×bulk density (EDANA method)).

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+3.6angle of repose+3.5angle of difference+7.9compressibility rate+290bulk density (EDANA method)).