PROBLEM TO BE SOLVED: To provide a vibration damping device which can be used in a rotor integrally equipped with rotor blades, is effective for periodical push-in actions and aperiodical perturbation, and also is effective for vibration of rotor blade having middle or low grade aspect ratio. SOLUTION: Rotor steps 32 for a gas turbine engine include a rotor disc and a plurality of rotor blades 36. The rotor disc is provided with a hole centering on the axis of rotation and a surface 40 in radial direction on the outside. The rotor blades 36 are extended from the surface 40 in radial direction on the outside to the outside in the radial direction and are distributed around the surface 40. At least one rotor blade 36 is positioned aslant (α) selectively relative to other adjacent rotor blade 36. This slant rotor blade increases the aerodynamic damping of the rotor steps.