PURPOSE: To prevent air bubbles from being enfolded as well as to keep off any disconnection due to arc discharge, by installing annular jets on an outer circumference of a center jet of machining fluid jet nozzle in a multistage manner, and making the center jet pressure stronger but the outer circumferential jet pressure weaker.

CONSTITUTION: A machining fluid jet nozzle 4 is made up of forming annular jets 42 and 43 on an outer circumference of a center jet 41 in a multistage manner. Jetting from the center jet 41 is carried out with strong pressure (for example, 50W100kg/cm2), insomuch that it can feed and flow up to the center of a work body, and each pressure of these annular jets 42 and 43 is made so as to have the following difference that the jet 42 is 1W5kg/cm2 and the jet 53 is 0.5W1kg/cm2 or so, respectively. With this constitution, enfoldment of air bubbles from the surroundings is prevented from occurring.