A method of dividing a silicon wafer along predetermined dividing lines, comprising a deteriorated layer forming step for forming deteriorated layers exposed to at least a surface to which a laser beam is applied, from the inside of the silicon wafer by applying a pulse laser beam with a wavelength capable of passing through the silicon wafer to the silicon wafer along the dividing lines; and a dividing step for dividing the silicon wafer along the dividing lines by applying a laser beam having absorptivity for the silicon wafer to the silicon wafer along the dividing lines where the deteriorated layers have been formed, from the side to which the deteriorated layers have been exposed, to generate thermal stress along the dividing lines.