Method for selecting the polarization of the laser beam inside a laser cavity, which provides generation of a laser beam (1) inside said resonant laser cavity (20), comprising optical media (8,10,9;9',12;9',14;13;33), which include one or more birefringent optical media (9;12;14;13). According to the invention, said birefringent optical media (9;12;14;13) are used for inducing a double refraction effect on the laser beam (1) and separating the propagation directions of the different polarization components (2,3) of the laser beam (1) at the interface (22;32;41,42;51,52;61,62) between said media (9;12;14;13) and a second medium with a different refractive index, providing a plurality of separate resonance directions (6,7) which are distinct for the different polarization components (2, 3), and selectively align the cavity optical axis (20) on one of said resonance positions (6,7) through the adjustment of the position of one or more optical elements (8,9,10;9',12;9',14;13,33) forming said cavity (20).