An objective of the present invention is to provide a laser capable of producing a radially polarized laser beam with an annular cross section. A laser oscillator 60 including an active layer 53 and two-dimensional photonic crystal 55 with circular holes 552 arranged in a square lattice pattern is provided between two electrodes 571 and 572. A first polarization control layer 581, which functions as a half-wave plate, and a second polarization control layer 582, which functions as a half-wave plate with a fast axis 592 extending at an angle of 45° to that of the first polarization control layer 581, are located on the laser oscillator 60. When a voltage is applied between the electrodes, a circumferentially polarized annular laser beam is emitted from the laser oscillator 60. When passing through the first polarization control layer 581 and the second polarization control layer 582, the laser beam is converted to a radially polarized beam. The resultant laser beam can be converged by a focusing lens to achieve a diameter smaller than the diffraction limit. Such a narrow beam is suitable for an optical pickup or many other devices.