A method of patterning a thin film is provided. The method includes coating a thin film layer and photoresist on a surface of a substrate; forming a first partially cured zone by performing a first exposing process of the photoresist with a mask, wherein exposing energy applied to the photoresist of the first partially cured zone is less than a photosensitive threshold of the photoresist; forming a cured zone on the first partially cured zone by performing a second exposing process of the photoresist with the mask, wherein a width of the cured zone is less than a width of the first partially cured zone, and exposing energy applied to the photoresist of the cured zone is equal to or greater than the photosensitive threshold of the photoresist; developing the photoresist; etching the thin film layer that is not covered by the photoresist; and removing the photoresist of the cured zone.