A light-guiding device that converts an input beam bundle made of a plurality of laser beams that have respectively been emitted from a plurality of LD elements, to an output beam bundle made of a plurality of output beams, includes a plurality of double mirrors each corresponding to a corresponding one of the LD elements LDi, the double mirrors being separated from one another. The double mirrors Mi each are made of a first mirror Mi1 that is mounted on a top surface of a base plate B and a second mirror Mi2 that is mounted on a top surface the first mirror Mi1. The first mirror has a first reflective surface whose normal makes an angle of 45° with a normal of the top surface of the base plate. The second mirror has a second reflective surface whose normal makes an angle of 135° with the normal of the top surface of the base plate. The laser beams respectively emitted from the LD elements respectively corresponding to the double mirrors each are first reflected by the first reflective surface and then further reflected by the second reflective surface. By adjusting orientations and positions of the first mirror and the second mirror, it is possible to adjust a propagation direction of each of the output beams.