A method of dividing a
wafer having a plurality of devices, which are formed in a plurality of areas sectioned by streets formed in a lattice pattern on the front surface and test
metal patterns which are formed on the streets, comprising: a
metal pattern breaking step for forming a break line in the test
metal patterns by applying a pulse
laser beam having permeability to the
wafer to the rear surface of the
wafer with its focal
point set to a position near the test metal patterns; a deteriorated layer forming step for forming a deteriorated layer along the streets above the break lines in the inside of the wafer by applying a pulse
laser beam having permeability to the wafer to the rear surface of the wafer with its focal
point set to a position above the break lines in the inside of the wafer; and a dividing step for dividing the wafer into individual chips along the deteriorated
layers of the wafer by exerting external force to the wafer having the deteriorated
layers formed therein.