A laser processing method for a nonlinear crystal substrate having a plurality of crossing division lines which includes the step of applying a pulsed laser beam to a work surface of the nonlinear crystal substrate along the division lines to thereby form a plurality of laser processed grooves on the work surface along the division lines. The pulse width of the pulsed laser beam is set to 200 ps or less and the repetition frequency of the pulsed laser beam is set to 50 kHz or less.