PURPOSE: To offer a method for dry cleaning of a semiconductor substrate contaminated by a heavy metal in a high-concentration degree by means of suppressing etching of the semiconductor substrate.

CONSTITUTION: Removal of a heavy metal is performed by making a chlorine radical to contact with a semiconductor substrate contaminated by a heavy metal, and removal of contamination of the semiconductor is so constituted that a temperature and a time where no contamination is generated, are experimentally decided, and with these experimentally decided temperature and time, a chlorine radical is made to contact with a substrate of the same kind with the substrate of aforesaid semiconductor. Further, a spectrum of an element constituting aforesaid semiconductor to be contained in exhaust gas is detected during dry cleaning at the same time by using a spectrum detection device, and when this spectrum detecting device detects the spectrum of an element constituting the semiconductor, dry cleaning is finished.