For surface strengthening of blisk blades, a blade area of the blisk is completely inserted into a water bath (13), and a multitude of high-pressure water jets are injected into the water bath which are directed bilaterally and essentially vertically—and opposite to each other—to both blade sides. Cavitation bubbles imploding near the blade surface that are generated in the water bath on the periphery of the high-pressure water jets to produce micro jets upon imploding, exerting an effect on the blade surface, creating plastically formed depressions without sharp edges. An apparatus for performing the method includes a container (3), a jetting unit (6) having parallel spaced apart water-jet tubes (4) with nozzle openings connected to a high-pressure water conduit (5) to produce the high-pressure water jets.