A method of adjusting a drive mechanism for driving a movable portion, the drive mechanism including a ring gear and a plurality of drive devices , each of the plurality of drive devices including a pinion that meshes with the ring gear and a drive unit that drives the pinion , the method comprising: a measurement step of measuring backlashes between the ring gear and the plurality of drive devices ; a determination step of determining the positions of the plurality of drive devices with reference to the ring gear based on the backlashes measured in the measurement step; and an adjustment step of adjusting a position of the pinion based on a result of the determination step, characterized in that the measurement step includes at least: aligning the pinion of one of the plurality of drive devices to face a reference position in a circumferential direction of the ring gear and measuring a backlash between the ring gear and the said one of the plurality of drive devices whose pinion faces the reference position; and aligning the pinion of another one of the plurality of drive devices to face the reference position of the ring gear by revolving the plurality of the drive devices relative to the ring gear , the said another one of the plurality of drive devices being different from the said one of the plurality of drive devices whose backlash has been measured, and measuring a backlash between the ring gear and the said another one of the plurality of drive devices whose pinion faces the reference position. a measurement step of measuring backlashes between the ring gear and the plurality of drive devices ; a determination step of determining the positions of the plurality of drive devices with reference to the ring gear based on the backlashes measured in the measurement step; and an adjustment step of adjusting a position of the pinion based on a result of the determination step, characterized in that the measurement step includes at least: aligning the pinion of one of the plurality of drive devices to face a reference position in a circumferential direction of the ring gear and measuring a backlash between the ring gear and the said one of the plurality of drive devices whose pinion faces the reference position; and aligning the pinion of another one of the plurality of drive devices to face the reference position of the ring gear by revolving the plurality of the drive devices relative to the ring gear , the said another one of the plurality of drive devices being different from the said one of the plurality of drive devices whose backlash has been measured, and measuring a backlash between the ring gear and the said another one of the plurality of drive devices whose pinion faces the reference position. aligning the pinion of one of the plurality of drive devices to face a reference position in a circumferential direction of the ring gear and measuring a backlash between the ring gear and the said one of the plurality of drive devices whose pinion faces the reference position; and aligning the pinion of another one of the plurality of drive devices to face the reference position of the ring gear by revolving the plurality of the drive devices relative to the ring gear , the said another one of the plurality of drive devices being different from the said one of the plurality of drive devices whose backlash has been measured, and measuring a backlash between the ring gear and the said another one of the plurality of drive devices whose pinion faces the reference position. <EOS>