A method of aligning an optical fiber according to the present invention has a first step of aligning an optical fiber by moving the optical fiber and finding a position that maximizes the power of beam outputted from the optical fiber with the use of a power meter, and a second step of moving and aligning the optical fiber in the optical axis direction (direction Z) from the position in which the optical fiber has been as a result of the alignment in the first step in a manner that makes the degree of polarization of two laser beams K1 and K2 equal to or lower than a given level with the use of a polarimeter.