Quickly making changes to etching conditions suppresses the production yield of printed wiring boards from being deteriorated. Disclosed is a method comprising: an etching step that comprises: preparing a conductor-clad base material continuous in a certain direction, the conductor-clad base material (1) having an insulating layer and one or more conductive layers formed on main surfaces of the insulating layer; and subjecting a predetermined region of a conductor layer of one main surface of the conductor-clad base material (1) to an etching process thereby to form a wiring pattern (1a) to be of a product and an inspection pattern (1b) to be used for inspection; a measuring step that measures a line width of the inspection pattern after the etching step; and a control step that controls an etching condition in the etching step based on the measured line width.