A working object grinding method capable of grinding a working object reliably is provided. A working object 1 is irradiated with a laser beam while locating a converging point therewithin, so as to form a reformed region 7 in the working object 1 along a reformed-region forming line set at a predetermined distance inside from an outer edge of the working object 1 along the outer edge, and a rear face 21 of the working object 1 is ground. As a result, the reformed region 7 or fissures C1 extending therefrom can inhibit fissures generated in an outer edge portion 25 upon grinding the working object 1 from advancing to the inside, whereby the working object 1 can be prevented from fracturing.