In a driving force transmission mechanism in a motor type damper device, when a small AC synchronous motor rotates in one direction and a tooth-missing gear part of a tooth-missing gear engages with the first rack part of a rack member the rack member is moved upward to operate a baffle in an open direction and, when the tooth-missing gear part engages with the second rack part of the rack member, the rack member is moved downward to operate the baffle in a close direction. In this manner, even when the baffle and the rack member are operated in both directions, the tooth-missing gear is required to be rotated in only one direction and the rotation of the small AC synchronous motor is not required to be reversed. Therefore, the structure of a control circuit for the motor type damper device can be simplified.