A phase shifter which modulates the phase of incident light has a light-transmitting substrate such as a glass substrate, and a phase modulator such as a concavity and convexity pattern which is formed on the laser beam incident surface of the light-transmitting substrate and modules the phase of incident light. A light-shielding portion which shields light in the peripheral portion where the optical intensity distribution decreases of the phase modulator is formed on the laser beam incident surface or exit surface of the phase shifter, thereby shielding the peripheral light in the irradiation surface of the incident laser beam.