A substrate processing method includes an etching step of mounting a substrate on a surface of a rotatory table arranged in a vacuum chamber and supplying an etching gas into the vacuum chamber while rotating the rotary table to etch a film formed on a surface of the substrate. The etching step includes supplying the etching gas to the surface of the rotary table and supplying a purge gas from a plurality of purge gas supply units that are provided near a region where the etching gas is supplied, and controlling an etching amount of etching the film by independently varying a flow rate of the purge gas that is supplied from each of the plurality of purge gas supply units.