A method includes the following steps: S1, providing the insulating layer having an inclined face; S4, disposing a photomask so that in the photoresist, first and second exposure portions are exposedto light, and exposing the photoresist is to light through the photomask; S5, removing the first and the second exposure portions of the photoresist. On the assumption that in S4, light reflected at the metal thin film is focused between the first and the second exposure portions of the photoresist, the inclined face has a bending portion bending in one direction, the portion removed in S5 in thephotoresist due to light focus being continuous with the first and the second exposure portions. The second exposure portion includes continuously an avoidance portion that avoids the bending portionand an overlapping portion that overlaps with at least a portion other than the bending portion in the inclined face.