A method of manufacturing a thin quartz crystal wafer from a quartz crystal block which is cut from a crystal body of synthetic quartz crystal and has a flat principal surface, comprises the steps of (a) converging a laser beam at a region in said quartz crystal block at a predetermined depth from the principal surface thereof to cause multiphoton phenomenon state, thereby breaking Si—O—Si bonds of quartz crystal in said region to form voids in said region, and (b) peeling said thin quartz crystal wafer from a body of said quartz crystal block along said voids. The above process is repeatedly performed on one quartz crystal block to peel off a plurality of thin quartz crystal wafers successively from the principal surface of the quartz crystal block. Each of the thin quartz crystal wafers is divided into individual quartz crystal blanks for making quartz crystal units.