Abstract: The invention provides a rotary actuator having a cushion mechanism for stopping a vane at a rotational terminal end position in a cushioning manner. The cushion mechanism has a first opening for discharging an exhaust air pressed out from a cylinder hole by a rotating vane to an external portion without limiting a flow amount, a second opening for discharging the exhaust air to the external portion in a state of limiting a flow amount and a flow amount adjusting mechanism for limiting a flow amount, the flow amount adjusting mechanism being connected to the second opening, wherein the first opening is provided at a position sealed by the vane before the vane of a hole surface in the cylinder hole reaches a rotational terminal end position, and the second opening is provided at a position which is not sealed by the vane after the vane reaches the rotational terminal end position.