A manufacturing method for a photomask for wafer processing includes a step of forming a groove on the front side of a light shielding plate in an area where light is to be passed. The groove has a depth not reaching the back side of the light shielding plate. A uniting step applies a bonding agent capable of transmitting light to the front side of the light shielding plate after performing the groove forming step and next attaching a transparent plate through the bonding agent to the front side of the light shielding plate to thereby unite the light shielding plate and the transparent plate. A grinding step holds the transparent plate on a chuck table after performing the uniting step. The back side of the light shielding plate is ground until the groove is exposed to the back side of the light shielding plate.