To provide a device for reproducing and recording information in a recording medium such as a DVD, CD, and CD-R/RW having different recording densities by means of only an inexpensive laser diode with a low recording density.

A laser beam from a laser diode 12 is made to pass a collimator lens 13 through a half mirror 11 and, a reflection mirror 15 is installed for guiding the beam to an objective lens 16 or 17, the laser beam is made incident to a disk 18 from the objective lens 16 or 17. The objective lens 16 has a high numerical aperture, while the objective lens 17 has a low numerical aperture. Immediately before the objective lens 16, there is arranged a super-resolution cut-off filter 10, both the lens 16 and the filter 10 are disposed in the optical path at the time of DVD reproduction. Also, the objective lens 17 is disposed in the optical path at the time of CD reproduction. The laser beam reflected from the disk 18 is received by a photodetector 90 that converts the beam to an electric signal.