A method of processing a device wafer includes the steps of applying a water-soluble protective film agent to a face side of the device wafer to form protective films thereon for protecting devices and leaving projected dicing lines exposed, dry-etching the device wafer through the protective films with a dry etching apparatus, recording a time when the water-soluble protective film agent is applied to the device wafer, confirming that the device wafer with the protective films formed thereon has been introduced into the dry etching apparatus, and issuing a warning if the introduction of the device wafer into the dry etching apparatus is not confirmed upon elapse of a predetermined time from the recorded time.