A photomask includes, on a translucent substrate, three or more first light-shielding portions each in insular shape having a property of shielding exposure light and spaced equidistantly, a second light-shielding portion having a property of shielding the exposure light and formed to connect the adjacent first light-shielding portions, and first light-transmitting portions each in slit shape having a property of transmitting the exposure light and formed to be surrounded with the first and second light-shielding portions. The second light-shielding portion is formed to contain a point located equidistantly from the three or more first light-shielding portions.