An etching fault is suppressed by use of an etching gas containing iodine heptafluoride. Provided is an attached substance removing method of removing an attached substance containing an iodine oxide attached to a component included in a chamber or a surface of a pipe connected with the chamber by use of a cleaning gas containing a fluorine-containing gas. Also provided is a dry etching method, including the steps of supplying an etching gas containing an iodine-containing gas into a chamber to perform etching on a surface of a substrate; and after the etching is performed on the surface of the substrate, removing an attached substance containing an iodine oxide attached to a component included in the chamber or a surface of a pipe connected with the chamber by use of a cleaning gas containing a fluorine-containing gas.