An LD module comprising: a plurality of laser diodes (LD1-LD10) forming a laser diode array; a plurality of fast axis collimating lenses (FAC1-FAC10) provided on optical paths of a plurality of laser beams emitted from the corresponding plurality of laser diodes (LD1-LD10); a plurality of mirrors (M1-M10) which reflect the plurality of laser beams emitted from the corresponding plurality of laser diodes (LD1-LD10), in slow axis directions of the laser beams, each mirror (M1-M10) having a respective first mirror comprising a first reflection surface, and a second mirror comprising a second reflection surface; and a fast axis focusing lens which focuses the plurality of laser beams reflected by the plurality of mirrors (M1-M10), so that the plurality of laser beams cross each other; the plurality of mirrors (M1-M10) being configured such that: the first mirrors each reflecting, in a fast axis direction, a corresponding one of the laser beams entering the mirrors (M1-M10); and the second mirrors each reflecting, in a slow axis direction, the corresponding one of the laser beams reflected by the first mirrors, the plurality of laser beams being such that a fast axis of a corresponding one of the laser beams entering the first mirrors is parallel to a slow axis of a corresponding one of the laser beams exiting from the second mirrors, characterized by each of the plurality of laser diodes (LD1-LD10) being inclined by a respective rotation angle about a vertical y-axis such that the plurality of laser diodes (LD1-LD10) emitting the plurality of laser beams toward the corresponding plurality of mirrors (M1-M10) in a slightly dispersed state so that distances between adjacent ones of the laser beams gradually increase,each of the plurality of mirrors (M1-M10) being tilted to the corresponding laser beam entering the respective mirror (M1-M10) such that the first reflection surface of the respective first mirror is substantially parallel to the slow axis of the incident laser beam, wherein the plurality of mirrors (M1-M10) reflect the plurality of laser beams in a slightly focused state toward the fast axis focusing lens so that distances between adjacent ones of the laser beams gradually decrease. a plurality of laser diodes (LD1-LD10) forming a laser diode array; a plurality of fast axis collimating lenses (FAC1-FAC10) provided on optical paths of a plurality of laser beams emitted from the corresponding plurality of laser diodes (LD1-LD10); a plurality of mirrors (M1-M10) which reflect the plurality of laser beams emitted from the corresponding plurality of laser diodes (LD1-LD10), in slow axis directions of the laser beams, each mirror (M1-M10) having a respective first mirror comprising a first reflection surface, and a second mirror comprising a second reflection surface; and a fast axis focusing lens which focuses the plurality of laser beams reflected by the plurality of mirrors (M1-M10), so that the plurality of laser beams cross each other; the plurality of mirrors (M1-M10) being configured such that: the first mirrors each reflecting, in a fast axis direction, a corresponding one of the laser beams entering the mirrors (M1-M10); and the second mirrors each reflecting, in a slow axis direction, the corresponding one of the laser beams reflected by the first mirrors, the plurality of laser beams being such that a fast axis of a corresponding one of the laser beams entering the first mirrors is parallel to a slow axis of a corresponding one of the laser beams exiting from the second mirrors, characterized by each of the plurality of laser diodes (LD1-LD10) being inclined by a respective rotation angle about a vertical y-axis such that the plurality of laser diodes (LD1-LD10) emitting the plurality of laser beams toward the corresponding plurality of mirrors (M1-M10) in a slightly dispersed state so that distances between adjacent ones of the laser beams gradually increase,each of the plurality of mirrors (M1-M10) being tilted to the corresponding laser beam entering the respective mirror (M1-M10) such that the first reflection surface of the respective first mirror is substantially parallel to the slow axis of the incident laser beam, wherein the plurality of mirrors (M1-M10) reflect the plurality of laser beams in a slightly focused state toward the fast axis focusing lens so that distances between adjacent ones of the laser beams gradually decrease.