A device includes a front cover, a torque converter main body, a lock-up device, and a dynamic damper. The dynamic damper is fixed to an output plate of the lock-up device. The dynamic damper has a base plate, an inertial body that includes inertia rings and lid members, and an elastic unit. The base plate is fixed to the output plate. The inertial body can rotate relative to the base plate. The elastic unit can generate a variable hysteresis torque according to a relative rotation angle difference between the base plate and the inertial body, and couples the base plate and the inertial body elastically in a rotation direction.