A damper device 10Y includes first inner springs SP1' configured to transmit a torque between a drive member 11Y and an intermediate member 12Y, second inner springs SP2' configured to transmit a torque between the intermediate member 12Y and a driven member 15Y, and a rotary inertia mass damper 20Y including a sun gear 22 serving as a mass body rotating with relative rotation of the drive member 11Y to the driven member 15Y. The rotary inertia mass damper 20Y is provided in parallel to a torque transmission path TP including the intermediate member 12Y, the first inner springs SP1' and the second inner springs SP2'. A damping ratio ¶ of the intermediate member 12 determined based on a moment of inertia J 2 of the intermediate member 12Y and rigidities k 1 and k 2 of the first and the second inner springs SP1' and SP2' is less than a value 1.