A mask including patterned structures arranged sequentially along a predetermined direction and a peripheral area surrounding the patterned structures is provided. Each of the patterned structures includes an opening portion and a thinning portion surrounding the opening portion. The opening portion has through holes arranged in a matrix. An outline of the thinning portion has two side edges opposite to each other substantially parallel to the predetermined direction. The thinning portion is defined by an area demarked by the outline of the thinning portion and an outline of the opening portion. A thickness of the thinning portion is thinner than a thickness of the peripheral area.