The semiconductor laser unit comprises a laser emission part having a plurality of semiconductor laser elements of different laser beam wavelengths, and a mirror part having an optical reflection film for reflecting laser beams emitted from the laser emission part. The mirror part is blocked out into a plurality of areas to which each laser beam emitted from each of the plurality of semiconductor laser elements enters, and at the same time the reflection film having high reflectance for the laser beams that enter selectively on the areas is provided in each of the plurality of areas.