Pneumatic rotary actuator that generates rotational motion using compressed air as power source. Rotation-specific pneumatic cylinder used in manufacturing line automation for workpiece rotational positioning, index table indexing, valve opening/closing, and fixture rotational clamping. Features angle control capability enabling precise rotational operation at set angles such as 90°, 180°, 360°. Available in various drive types including vane type, rack and pinion type, and helical spline type, with important specification selection for torque, rotation angle, and rotation speed. Rotation-specific actuator with structure and applications clearly different from standard linear motion cylinders.