Laser processing method for wafer

A processing method for a wafer having a device area where a plurality of devices are formed and a peripheral marginal area surrounding said device area, said plurality of devices being respectively formed in a plurality of regions partitioned by a plurality of division lines formed on a front side of said wafer, said processing method comprising:

• a modified layer forming step of holding said wafer on a chuck table in the condition where a back side of said wafer is exposed and applying a laser beam having a transmission wavelength to said wafer toward the back side of said wafer along said division lines in the condition where the focal point of said laser beam is set inside said wafer, thereby forming a modified layer as a division start point inside said wafer along each division line;
• and
• a transporting step of unloading said wafer from said chuck table and transporting said wafer to a position where a step to be next performed;
• wherein said modified layer is not formed in said peripheral marginal area of said wafer in said modified layer forming step to thereby form a reinforcing portion in said peripheral marginal area;
• wherein:
• said wafer comprises an optical device wafer composed of a sapphire substrate and a plurality of optical devices formed on a front side of said sapphire substrate in a plurality of regions partitioned by a plurality of division lines;
• and
• said step to be next performed after performing said transporting step includes a back processing step of forming a reflection film on a back side of said optical device wafer.