A blue-violet emission point, an infrared emission point, and a red emission point in a semiconductor laser apparatus are arranged so as to be arranged in this order on a substantially straight line along a first direction. A blue-violet laser beam emitted from the blue-violet emission point and a red laser beam emitted from the red emission point are incident on an optical disk by an optical system comprising a polarizing beam splitter, a collimator lens, a beam expander, a .lamda./4 plate, an objective lens, a cylindrical lens, and an optical disk, is returned from the optical disk, and is introduced into an photodetector. The infrared laser beam emitted from the infrared emission point is incident on the optical disk by the optical system, is returned from the optical disk, and is introduced into the photodetector.