To provide a method and an apparatus for cleaning a chamber for preventing dust from adhering to the materiel to form an IC pattern on.

In the case the counted number of a particle counter 15 exceeds an allowable value when a gate valve 17 and a material transporting in and out valve 18 are closed, a control apparatus 14 is put in a cleaning mode and transmits instructions to valve driving mechanisms 12, 13 to operate a vent valve 10 and an exhaust valve 8 in such a manner that the valves mutually synchronously an repeatedly open and close for every prescribed period. Due to the mutually synchronized opening and closing operation, rapid venting and rapid exhaust are repeated. When the detected value of the particle counter 15 becomes a value within the allowable range during the repeat of the opening and closing, the control apparatus 14 stops the cleaning and the cleaning of a spare chamber is completed.