To provide a rotor blade device for a missile capable of improving the degree of freedom of layout of a rotor blade and a rotary shaft and miniaturizing a driving device by minimizing a load applied to the driving device while coping with the movement of the aerodynamic center without limiting the layout of the rotor blade and the rotary shaft in a missile capable of supersonically flying.

When a missile 1 is in a subsonic region, the aerodynamic center O is located substantially at the center of a rotor blade 4 (a), and the aerodynamic center O moves to the rear side of the rotor blade 4 by accelerating in a supersonic region from a transonic region, whereas a first valve 20 is opened to supply a hydraulic fluid to a cylinder part 4a of the rotor blade 4 to move the rotor blade 4 forward relative to the rotary shaft 6 to thereby maintain the aerodynamic center O on a rotation axis A (b). When the aerodynamic center returns into the original position in decelerating, a second valve 22 is opened to release oil pressure to thereby return the rotor blade 4 into the original position (c).