Abstract: A plurality of eccentric rotors are rotatably fitted between a fixed base and an output shaft on which an object to be vibrationproofed is mounted, the output shaft being supported movably in 3 to 6 Degree-of-Freedom, magnet spring mechanisms are provided on fitted wall surfaces between the fixed base and the eccentric rotor, a composite vibrationproof adjusting spring is provided between the fixed base and the output shaft, the magnet spring mechanism responding to a fine displacement of the output shaft, and in a case where the output shaft is greatly displaced, the output shaft is braked so as to be restored to a predetermined position by the composite vibrationproof adjusting spring mechanism. The magnet spring mechanism produces a large braking force since a rotational angle is large and a rotational-angle speed is high due to eccentricity of eccentric rotors.