The hologram recording technology expected to realize ultrahigh-density information recording is one of the post Blu-ray Disc technology. When we think about developing a drive based on this technology and suitable for consumer electronics, it is considered most desirable from the viewpoint of upward compatibility to solve the problem of the BD-compatibility. The problem in sharing the laser light source between the hologram recording device and the current optical disc device, however, is that the hologram recording requires a high-coherent, single-mode light beam, while the current optical discs requires a low-coherent, multi-mode light beam. In point of the coherence of the light source, the above two cases require the light beams of the characteristics opposite to each other, and this presents an important task.For the purpose of solving the above-mentioned problem, the present invention is to adopt the variable wavelength type laser light source device composed of a semiconductor laser and a diffraction grating, wherein a polarization direction converter and a polarized beam splitter are placed in the optical path between the above semiconductor laser and the above diffraction grating.