Abstract: The present invention provides a system 1A for supplying processing water 3, which is used in the operation of processing a target object with a highly pressurized jet of processing water 3 containing an abrasive, including: a tank 2 for storing the processing water 3, having a lower portion substantially tapering downwards; a supply pipe 5 for supplying the processing water 3 to the tank 2; a delivery pipe 8 having an opening 9 located inside the tank 2; a pressure mechanism 7 located outside the tank 2, for pressurizing the processing water 3; and a suction port 10 provided in the side surface of the delivery pipe 8. The processing water 3 in the tank 2 is stratified into a deposition portion 4A, which is a portion where the abrasive is deposited, and a clear-water portion 4W, which is a portion other than the deposition portion 4A and formed by clear water substantially free from the abrasive.