The method is used for manufacturing a blade (201) of a turbomachine comprising an airfoil portion (202); according thereto at least one external or internal surface of the airfoil portion is obtained by wire electric discharge machining; this is allowed by designing these surfaces as "ruled surfaces" or very close to such kind of surfaces; this method is particularly effective, for forming internal cavities (205) of hollow stator blades of steam turbines; this method allows to manufacture in a single piece hollow blades (201) having root portions and shroud portions. Blade of a turbomachine with an internal cavity wherein the surface of the airfoil of the blade inside the cavity defines grooves perpendicular to the axis of the turbomachine.