A laser beam-combining optical device according to the present invention includes a plurality of semiconductor laser arrays, and a reflective element that reflects a laser light beam emitted from at least one semiconductor laser array of the plurality of semiconductor laser arrays. When laser light beams emitted from respective ones of the plurality of semiconductor laser arrays are focused on a single focus point, the laser light beam emitted from the at least one semiconductor laser array is reflected by the reflective element, and is then focused on the focus point.