Abstract: A manufacturing method of an element chip includes a preparation process of adhering a holding sheet to the first main surface of a substrate so as to prepare the substrate held by the holding sheet, a plasma dicing process of performing plasma etching on the isolation region of the substrate to the first main surface so as to divide the substrate into the plurality of element chips. The plasma dicing process includes a first plasma etching process of performing plasma etching on a the isolation region partially in a thickness direction while a cooling gas is supplied between the stage and the holding sheet, and a second plasma etching process of stopping a supply of the cooling gas after the first plasma etching process, and performing plasma etching on a remaining portion of the isolation region.