An optical axis adjusting apparatus for a laser apparatus, the optical axis adjusting apparatus comprising: a modulated light beam generating unit which includes a light source and a coupling lens to release a light beam to irradiate the released light beam to a detection target; multiple light receiving devices (4a, 4b, 4c) which receive light reflected from the detection target; and a reflected light collecting unit which collects light reflected from the detection target to guide the collected light to the multiple light receiving devices (4a, 4b, 4c); characterized by: first and second targets (9; 59a, 59b; 99a, 99b), wherein: the multiple light receiving devices (4a, 4b, 4c) are arranged along a vertical direction relative to a releasing direction of the light beam such that the detection target is divided into multiple detection regions (11a, 11b, 11c), the first target (59a; 99a) and the second target (59b; 99b) are arranged such that a distance thereto from the laser apparatus in an emitting direction of the light beam mutually varies, a width in a vertical direction relative to the emitting direction of the light beam of the first target (59a; 99a) is formed to be smaller than an irradiating width in the vertical direction of the light beam, one of the multiple light receiving devices (4a, 4b, 4c) is installed at a position which receives only a reflected light from the first target (59a; 99a), and the other (4a, 4c) of the multiple light receiving devices (4a, 4b, 4c) are installed at positions which receive only a reflected light from the second target (59b; 99b). a modulated light beam generating unit which includes a light source and a coupling lens to release a light beam to irradiate the released light beam to a detection target; multiple light receiving devices (4a, 4b, 4c) which receive light reflected from the detection target; and a reflected light collecting unit which collects light reflected from the detection target to guide the collected light to the multiple light receiving devices (4a, 4b, 4c); characterized by: first and second targets (9; 59a, 59b; 99a, 99b), wherein: the multiple light receiving devices (4a, 4b, 4c) are arranged along a vertical direction relative to a releasing direction of the light beam such that the detection target is divided into multiple detection regions (11a, 11b, 11c), the first target (59a; 99a) and the second target (59b; 99b) are arranged such that a distance thereto from the laser apparatus in an emitting direction of the light beam mutually varies, a width in a vertical direction relative to the emitting direction of the light beam of the first target (59a; 99a) is formed to be smaller than an irradiating width in the vertical direction of the light beam, one of the multiple light receiving devices (4a, 4b, 4c) is installed at a position which receives only a reflected light from the first target (59a; 99a), and the other (4a, 4c) of the multiple light receiving devices (4a, 4b, 4c) are installed at positions which receive only a reflected light from the second target (59b; 99b). first and second targets (9; 59a, 59b; 99a, 99b), wherein: the multiple light receiving devices (4a, 4b, 4c) are arranged along a vertical direction relative to a releasing direction of the light beam such that the detection target is divided into multiple detection regions (11a, 11b, 11c), the first target (59a; 99a) and the second target (59b; 99b) are arranged such that a distance thereto from the laser apparatus in an emitting direction of the light beam mutually varies, a width in a vertical direction relative to the emitting direction of the light beam of the first target (59a; 99a) is formed to be smaller than an irradiating width in the vertical direction of the light beam, one of the multiple light receiving devices (4a, 4b, 4c) is installed at a position which receives only a reflected light from the first target (59a; 99a), and the other (4a, 4c) of the multiple light receiving devices (4a, 4b, 4c) are installed at positions which receive only a reflected light from the second target (59b; 99b). the multiple light receiving devices (4a, 4b, 4c) are arranged along a vertical direction relative to a releasing direction of the light beam such that the detection target is divided into multiple detection regions (11a, 11b, 11c), the first target (59a; 99a) and the second target (59b; 99b) are arranged such that a distance thereto from the laser apparatus in an emitting direction of the light beam mutually varies, a width in a vertical direction relative to the emitting direction of the light beam of the first target (59a; 99a) is formed to be smaller than an irradiating width in the vertical direction of the light beam, one of the multiple light receiving devices (4a, 4b, 4c) is installed at a position which receives only a reflected light from the first target (59a; 99a), and the other (4a, 4c) of the multiple light receiving devices (4a, 4b, 4c) are installed at positions which receive only a reflected light from the second target (59b; 99b).