To provide a working fluid feeding device of a wire saw, which reduces the amount of working fluid usage and improves the machining ability and machining accuracy of the wire saw, by making the working fluid efficiently adhere to a wire.

The wire saw functions to cut a workpiece 5 by pressing the same to the reciprocating wire 2 in a perpendicular direction while feeding the working fluid to the wire 2. The working fluid feeding device is composed of a working fluid introducing guide 13 which is arranged between a working fluid feeding nozzle 11 for ejecting the working fluid and a wire row 4, for introducing the working fluid ejected from the working fluid feeding nozzle 11, on an upper surface of the wire 2 in the vicinity of a machining point 15.