A cleaning method of a substrate processor that reduces damage to a member in a substrate processing container. The method of cleaning the substrate processing container of the substrate processor that processes a target substrate according to the present invention includes: introducing gas into a remote plasma generating unit of the substrate processor; exciting the gas by the remote plasma generating unit, and generating reactive species; and supplying the reactive species to the processing container from the remote plasma generating unit, and pressurizing the processing container at 1333 Pa or greater.