A dynamic damper device includes a variable inertial mass device that variably controls inertial mass of a damper mass, an elastic body that connects a rotary shaft rotated by power transmitted thereto and an input member of the variable inertial mass device, and a variable damping force device that variably controls a damping force to the elastic body. Accordingly, the dynamic damper devices have the advantageous effect that vibrations can be appropriately reduced.