A torsional vibration damping device, comprising: a first rotation member; a second rotation member arranged at a radially outside of the first rotation member; at least one or more resilient members disposed between the first rotation member and the second member, the at least one or more resilient members being deformed resiliently between the first rotation member and the second member upon relative rotation between the first rotation member and the second rotation member; a cam portion arranged on a radially outer peripheral portion of the first rotation member and having a cam surface that is configured to vary its curvature along its circumferential direction; and an arm member whose one end portion is in contact with an outer peripheral portion of the cam portion, the other end portion being urged by the resilient member, the arm member being brought into rotation about a rotation fulcrum formed on the second rotation member to deform the resilient member resiliently upon the relative rotation between the first rotation member and the second rotation member, the rotation of the arm member allowing for transmission of a rotational torque between the first rotation member and the second rotation member, the arm member being interposed, as only one arm member, between the first rotation member and the one resilient member, characterized in that the second rotation member, which is arranged at the radially outside of the first rotation member, surrounds the resilient member, the arm member, and the cam portion, thereby defining a space in which a lubricant is accommodated between a radially outer peripheral portion of the first rotation member and an axially inner peripheral portion of the second rotation member, a sealing member is interposed between a radially inner peripheral portion of the second rotation member and the radially outer peripheral portion of the first rotation member, and the first rotation member and the cam member are formed therein with a communication hole for establishing a fluid communication between the space and an outside of the space. a first rotation member; a second rotation member arranged at a radially outside of the first rotation member; at least one or more resilient members disposed between the first rotation member and the second member, the at least one or more resilient members being deformed resiliently between the first rotation member and the second member upon relative rotation between the first rotation member and the second rotation member; a cam portion arranged on a radially outer peripheral portion of the first rotation member and having a cam surface that is configured to vary its curvature along its circumferential direction; and an arm member whose one end portion is in contact with an outer peripheral portion of the cam portion, the other end portion being urged by the resilient member, the arm member being brought into rotation about a rotation fulcrum formed on the second rotation member to deform the resilient member resiliently upon the relative rotation between the first rotation member and the second rotation member, the rotation of the arm member allowing for transmission of a rotational torque between the first rotation member and the second rotation member, the arm member being interposed, as only one arm member, between the first rotation member and the one resilient member, characterized in that the second rotation member, which is arranged at the radially outside of the first rotation member, surrounds the resilient member, the arm member, and the cam portion, thereby defining a space in which a lubricant is accommodated between a radially outer peripheral portion of the first rotation member and an axially inner peripheral portion of the second rotation member, a sealing member is interposed between a radially inner peripheral portion of the second rotation member and the radially outer peripheral portion of the first rotation member, and the first rotation member and the cam member are formed therein with a communication hole for establishing a fluid communication between the space and an outside of the space.