In a method of fabricating element chips, a method of forming a mask pattern, and a method of processing a substrate, a process sequence is set such that developing in which the exposure-ended protection film is patterned is performed, after grinding in which the substrate is thinned by grinding a second surface opposite to a first surface to which a photosensitive protection film is pasted. Thereby, it is possible to perform the grinding for thinning in a state where the protection film is stable without being patterned, and to prevent the substrate or the protection film on which a mask pattern of the substrate is formed from being damaged at the time of the grinding, even in a case where a thin substrate of a wafer shape becomes a target.