A object cutting method includes a first step of attaching an expandable sheet to a front surface or a back surface of a object, a second step of irradiating the object with a laser light along a line to cut to form a modified region, and expanding the expandable sheet to divide at least a part of the object into a plurality of chips and to form a gap that exists between the chips and extends to a side surface crossing the front surface and the back surface of the object, a third step of, after the second step, filling the gap with a resin from an outer edge portion including the side surface of the object, a fourth step of, after the third step, curing and shrinking the resin, and a fifth step of, after the fourth step, taking out the chips from the expandable sheet.