To lessen the load on an operator and clean at good timings by cleaning a film-forming chamber, when a specified number of treated wafers having forming films is reached.

Before film forming is made on wafers, the number of wafers to be cleaned is inputted to an input unit 22a to register cleaning conditions, including this number of wafers in a sequencer 25, a substrate sensor detects the number of wafers treated in a treating chamber, the sequencer 25 counts the number of wafers having formed films, based on the output of the substrate sensor. In a specified number of treated wafers is reaches, it is so set that a cleaning of the treating chamber is made. Thus the cleanings are made with good timings, without increasing the load of the operator, and the scratches of the wall surface, etc., of the treating chamber is avoided.