A laser apparatus 10 includes: a laser medium 11 arranged between a pair of reflecting means 12A and 12B of an optical resonator 12 and adapted to be excited to emit light; a saturable absorber 14 arranged on the optical axis L of the optical resonator 12 between the pair of reflecting means, the transmissivity thereof being adapted to increase with the absorption of emitted light 21 from the laser medium; and an excitation light source unit 13 adapted to output light 22 having a wavelength that excites the laser medium. The saturable absorber 14 is a crystalline body having first to third mutually perpendicular crystallographic axes and is arranged in the optical resonator 12 in such a manner as to have different transmissivities for emitted light in two mutually perpendicular polarization directions. In this case, a laser oscillation occurs for emitted light in the polarization direction that shows the greater transmissivity, and it is therefore possible to obtain laser beams having a stabilized polarization direction.