The present invention pertains to an optical axis alignment method for an optical device, and the like. In the present invention, optical axis adjustment can be performed with high accuracy and in a short amount of time by a method that includes the following. Initially, images of a lens holder and a holder base are captured to acquire information regarding an external shape prior to laser light radiation (Q1). Next, position information regarding light beams projected from a collimator lens is detected (Q2). Laser light is radiated to cause plastic deformation and the position of the collimator lens is adjusted (Q3). Images of the lens holder and the holder base are captured to acquire new information regarding the external shape after laser light radiation (Q4). New position information regarding a light path, on which the light beams projected from the collimator lens travel, is detected (Q5). If the optical axis alignment is not within an allowable range, laser light radiation conditions are changed on the basis of the external shape information and/or position information obtained before and after laser light radiation (Q7), and lens position adjustment using laser light radiation (Q3) is repeated.