PURPOSE: To prevent turbulence of the ambiance in a clean room by providing a gas collecting port at the position surrounding near a gas chamber to form the balance of the positive pressure and the negative pressure operating depending on the Bernoulli's effect, and collecting the exhaust gas positively, and to provide a plate form noncontact holding device having a posistioning stopper which can be pulled out and pushed in so as to be inserted in a narrow space.

CONSTITUTION: A gas ejection nozzle 31 whose diameter is expanded toward the opening, an extending wall connected to the peripheral edge of the opening of the gas ejection nozzle 31, and an exhaust gas collecting port 22a provided on the line surrounding the ejection nozzle 31 at each extending wall or at one group of extending walls, are provided. A movable pin stopper device driven to the position projecting to the outer side of the extending wall surface, or buried in a plate from member 2, is provided at a necessary position of the extending wall.