<p>The purpose of the present invention is to provide a damper device that eliminates rattling in a spline coupling section between an inertial body and a shaft. The damper device comprises: a first shaft that outputs rotational force from a power source; a second shaft that transmits rotational force to a gear mechanism and has an external spline; a first rotating member to which the rotational force of the first shaft is transmitted; a second rotating member that spline-engages with the external spline; a damper section that absorbs torque variation between the first rotating member and the second rotating member; and an inertial body that has an internal spline that spline-engages with the external spline and has an annular section of a substantially annular shape. The gear section of the internal spline is pressed into contact with the gears of the external spline in the peripheral direction of the inertial body.</p>
