The invention relates to a method and a device for generating a jet of liquid which is suitable, in the manner of a waveguide, to carry a laser beam injected into it and which is used to process a work piece. Said device comprises a liquid nozzle for generating a jet of liquid and a gas outlet nozzle, disposed at a distance from the liquid nozzle and producing a flow of gas enclosing the jet of liquid on the exterior thereof. A gas storage is defined between the liquid nozzle and the gas outlet nozzle. The jet of liquid is passed or ejected through the gas outlet nozzle. The jet of liquid has a diameter of preferably 60 m or less and the flow of gas has a diameter of 1-2 mm.