A light-guiding device includes: a group of mirrors that converts a first beam bundle including a plurality of first laser beams into a second beam bundle including a plurality of second laser beams; a group of collimating lenses disposed at a stage previous to the group of mirrors and including collimating lenses that each collimate a divergence, in an F-axis direction, of a corresponding one of the plurality of first laser beams; and a converging lens disposed at a stage subsequent to the group of mirrors, the converging lens converges the second beam bundle by refracting each of the plurality of second laser beams.