In a vibration damping device 20, the following are determined: a moment of inertia J1 of a driven member 15; a moment of inertia J2 of an inertial mass body 23; a mass m of a crank member 22; a distance L3 between a center of gravity G of the crank member 22 and a fulcrum of swinging of the crank member 22 with respect to the inertial mass body 23; and a distance L4 between the fulcrum and a center of rotation RC. Such determination is carried out so that the torque variation of a damping target becomes a target value, the torque variation being derived on the basis of an angular displacementand an angle obtained by solving equations of motion for the driven member 15 and equations of motion for the entirety of the vibration damping device 20.