A method for controlling an air servo cylinder apparatus includes an advancing process of advancing a piston up to a target position by controlling, by a controller, servo valves individually connected to a pressure chamber on the head side and that on the rod side of the cylinder, and a pressurizing process of subsequently applying a required pressurizing force to the piston. In the advancing process, the piston starts to be driven with the servo valve on the head side opened to the air intake side and the servo valve on the rod side opened to the exhaust side. Thereafter, the opening degree of the servo valve on the rod side is varied into an opening degree in accordance with a deviation of the current position from the target position, and thereby the piston is smoothly decelerated as it approaches the target position.