A method of manufacturing a semiconductor device including a wafer using a plasma etching device which includes a chamber, a chuck provided in the chamber to dispose a wafer to be processed thereon, a focus ring disposed at a peripheral edge portion of the chuck, and a gas supplying mechanism configured to supply various types of gases depending a radial position of the wafer. The method includes: placing a wafer formed with an organic film on the chuck; introducing an etching gas which etches the organic film on the wafer from the process gas supplying mechanism to a central portion of the wafer; introducing an etching inhibiting factor gas having a property of reacting with the etching gas to the peripheral edge portion of the wafer from the gas supplying mechanism; and performing plasma etching on the wafer using the etching gas.