An optical axis adjusting method for adjusting a tilt angle of an optical axis in two regions optically coupled in a holding member includes the steps of: roughly adjusting the optical axis by irradiating a first region on the holding member with a laser beam; and finely adjusting the optical axis by irradiating a second region on the holding member with a laser beam. One of the two regions is set as a reference point. The first region is located closer to the reference point, while the second region is located further from the reference point.