A photomask forming method and a photomask. The photomask forming method comprises the following steps: providing a substrate, the substrate being provided with a chip area (33), and a first scribe line (31) and a second scribe line (32) located on the two opposite sides of the chip area (33); and forming a first group of marks in the first scribe line (31), and forming a second group of marks in the second scribe line (32), the first group of marks comprising first sub-mark groups and first intervals (25) which are alternately arranged in an extending direction of the first scribe line (31), the second group of marks comprising second sub-mark groups and second intervals (26) which are alternately arranged in an extending direction of the second scribe line (32), the first sub-mark groups and the second intervals (26) being arranged in an aligned manner, and the second sub-mark groups and the first intervals (25) being arranged in an aligned manner. According to the photomask forming method and the photomask, the requirement of respectively forming a group of marks in the scribe lines on the two opposite sides of the chip area (33) can be satisfied under the condition that the width of the scribe lines is narrow.