Method for treating inner surface of chlorine trifluoride supply path in device using chlorine trifluoride

This invention provides a method for treating the inner surface of a chlorine trifluoride supply path that enables the reliable suppression of drops in the concentration of ClF3 in a reaction chamber during the treatment work. A gas supply path (2) and a gas discharge path (3) are integrally connected to a treatment chamber (1) of a treatment device, in which the chlorine trifluoride is used as an etching gas. The chlorine trifluoride gas with a concentration equal to or greater than the concentration of the chlorine trifluoride gas supplied during the etching treatment operation is allowed to act on the inner surfaces of at least the treatment chamber (1) and the gas supply path (2) from the integrally formed treatment chamber (1), the gas supply path (2), and the gas discharge path (3), thus coating the inner surfaces of at least the treatment chamber (1) and the gas supply path (2) with a fluoride film.