An ashing system wherein variations in ashing rate over time are suppressed. The ashing system performing ashing of an organic material on a substrate (W) including an exposed metal in a processing chamber (11) includes a passage formed in the processing chamber (11) in which passage an active species supplied to the processing chamber (11) passes through. The passage is formed such that the same metal as the one scattered from the substrate (W) by the active species is exposed to the surfaces (11a; 31a; 33a; 33b) defining the passage and to which the metal scattered from the substrate (W) adheres.
