Provided is an active matrix substrate manufacturing method, including the steps of: selectively forming a laminated structure pattern, by forming the laminated structure on a glass substrate (2), by forming a first photosensitive resin pattern (PR) on the laminated structure, and by selectively forming the laminated structure pattern using the first photosensitive resin pattern (PR), the laminated structure including a metal layer (a scanning signal line (11) material), a gate insulative layer (30), and a semiconductor layer (31, 33) (transistor material); fluorinating a surface of the first photosensitive resin pattern (PR) by dry-etching with fluorine gas; applying a coating-type transparent insulative resin (60) onto the glass substrate (2) to fill a space in the laminated structure pattern; and removing the fluorinated first photosensitive resin pattern (PR). This enables to form, in an active matrix substrate manufacturing process, a scanning signal line and a semiconductor layer with a single mask process.