Substrate dividing method using an expansion tape and a roller

A substrate dividing method for dividing a substrate along streets into a plurality of chips, the substrate dividing method comprising:

• a substrate preparing step of preparing the substrate that is formed with division start points along the streets and that has a protective sheet attached to a surface on one side thereof;
• an expanding tape attaching step of rolling a roller on a surface on another side of the substrate, in a state in which the protective sheet side is held under suction on a holding table, to attach an expanding tape to the surface on the other side of the substrate;
• a crack extending step of, after the expanding tape attaching step is carried out, cancelling the suction by the holding table to form a gap between a holding surface of the holding table and the protective sheet, and then bringing the roller into contact with the expanding tape and rolling the roller on the expanding tape, causing the substrate to sink into the gap through the protective sheet with the division start points as starting points and the protective sheet to contact the holding surface, and extend cracks originating from the division start points;
• and
• a chip interval expanding step of, after the crack extending step is carried out, expanding the expanding tape to widen intervals of a plurality of chips with the division start points as starting points.