A wafer processing method includes forming a resist film on the front side of a wafer in an area except division lines, plasma etching the wafer to form a groove on the front side of the wafer along each division line, the groove having a depth greater than a finished thickness, removing the resist film from the front side of the wafer by cleaning, and grinding the back side of the wafer to reduce the thickness of the wafer to the finished thickness, so that the groove is exposed to the back side of the wafer to thereby divide the wafer into individual device chips. In the resist film removing step, a chemical fluid is sprayed to the resist film formed on the front side of the wafer, thereby removing the resist film.