A laser module , comprising: an optical fiber (OF); n laser diodes LD i (i = 1, 2, ..., n) arranged in this order in accordance with a descending order of an optical path length LO i , the optical path length LO i being a length of an optical path extending from each of the laser diodes LD i to the optical fiber (OF), wherein the n laser diodes LD i respectively emit laser beams LB i ; and n S-axis collimating lenses SL i provided in the respective optical paths so as to be distant from the respective laser diodes LD i and from the optical fiber (OF), each of the n laser diodes LDi and each of the n S-axis collimating lenses SLi constituting a part of n unit optical systems which respectively couple the laser beams LBi and a laser beam propagated through the optical fiber (OF), when a distance from each of the laser diodes LD i to a corresponding one of the S-axis collimating lenses SL i is defined to be a collimation length LC i , at least one of a collimation length LCi corresponding to a laser diode LDi and a collimation length LC n corresponding to a laser diode LD n differing from a certain distance SL so as to reduce the largest one of incident angles β i at which rays of a laser beam LBi or laser beam LB n enter the optical fiber (OF), the certain distance SL being a collimation length LC i of a reference unit optical system which is a unit system whose optical path length LO i has an intermediate value or a unit system whose optical path length LO i has a value closest to the intermediate value among the n unit optical systems, the certain distance SL being set such that respective optical paths of rays of a laser beam LB i emitted from the laser diodes LD i included in the reference unit optical system are parallel to one another or diverged after the rays have passed through a corresponding one of the S-axis collimating lenses SL i included in the reference unit optical system, and at least an S-axis collimating lens SL 1 being arranged so as to satisfy SL < LC 1 . an optical fiber (OF); n laser diodes LD i (i = 1, 2, ..., n) arranged in this order in accordance with a descending order of an optical path length LO i , the optical path length LO i being a length of an optical path extending from each of the laser diodes LD i to the optical fiber (OF), wherein the n laser diodes LD i respectively emit laser beams LB i ; and n S-axis collimating lenses SL i provided in the respective optical paths so as to be distant from the respective laser diodes LD i and from the optical fiber (OF), each of the n laser diodes LDi and each of the n S-axis collimating lenses SLi constituting a part of n unit optical systems which respectively couple the laser beams LBi and a laser beam propagated through the optical fiber (OF), when a distance from each of the laser diodes LD i to a corresponding one of the S-axis collimating lenses SL i is defined to be a collimation length LC i , at least one of a collimation length LCi corresponding to a laser diode LDi and a collimation length LC n corresponding to a laser diode LD n differing from a certain distance SL so as to reduce the largest one of incident angles β i at which rays of a laser beam LBi or laser beam LB n enter the optical fiber (OF), the certain distance SL being a collimation length LC i of a reference unit optical system which is a unit system whose optical path length LO i has an intermediate value or a unit system whose optical path length LO i has a value closest to the intermediate value among the n unit optical systems, the certain distance SL being set such that respective optical paths of rays of a laser beam LB i emitted from the laser diodes LD i included in the reference unit optical system are parallel to one another or diverged after the rays have passed through a corresponding one of the S-axis collimating lenses SL i included in the reference unit optical system, and at least an S-axis collimating lens SL 1 being arranged so as to satisfy SL < LC 1 . <EOS>