The present invention pertains to a hydrous silica for rubber-reinforcing filler, having a BET specific surface area ranging from 230 to 350 m2/g; the volume average particle diameter (D50) measured by the laser diffraction method after dispersing 50 ml of a hydrous silica slurry adjusted to 4% by weight with an ultrasonic homogenizer having an output of 140 W for 10 minutes is 3.0 μm or less; and the top 10% of particles (D90) in the particle size distribution is 10.0 μm or less. This invention provides a hydrous silica capable of further improving reinforcing properties of a rubber, particularly the wear resistance by improving dispersibility of the hydrous silica in the rubber in addition to rubber reinforcing properties obtained by a high BET specific surface area.