Dividing method for platelike workpiece

A method of dividing a platelike workpiece along a plurality of division lines formed on the front side of a substrate, wherein the front side of said substrate is partitioned into a plurality of chip regions by said division lines, and a metal layer is formed on the back side of said substrate, said method, comprising:

• a modified layer forming step of applying a laser beam having a transmission wavelength to said substrate along said division lines so that said laser beam is focused inside said substrate, thereby forming a modified layer in said substrate along each division line;
• an expansion tape attaching step of attaching an expansion tape to said metal layer of said workpiece before or after performing said modified layer forming step;
• a bending step of bending said workpiece along each division line toward said metal layer side after performing said modified layer forming step and said expansion tape attaching step, thereby dividing said substrate along each division line from the corresponding modified layer as a starting point and simultaneously forming a weak portion in said metal layer along each division line;
• and
• an expansion tape expanding step of expanding said expansion tape after performing said bending step, thereby dividing said metal layer along each division line from the corresponding weak portion as a starting point.