The invention provides a production method for an active matrix substrate in which a plurality of contact holes are formed by a one-mask process so as to reach metal films which are present at different depth positions in an insulating layer and are not evaporated by dry etching using a fluorine-containing gas. The method includes a step of performing dry etching using mixed gas of CHF3, CF4 and O2 to form the plurality of contact hole, a step of subjecting the plurality of contact holes to oxygen ashing, and a step of forming a transparent conductive film in the plurality of contact holes.