A wafer processing method includes: providing a wafer, wherein the wafer has a first position and a second position, and the first position faces the second position in a reference direction; coating a photoresist liquid on the wafer; and performing a heating process to heat the wafer coated with the photoresist liquid to form a photoresist layer on the wafer, wherein during the heating process, a temperature of the wafer gradually increases in the reference direction, so that a thickness of the photoresist layer gradually decreases in the reference direction.