To provide an optical system for optical disk which can suppress good various aberration caused at the time of recording and reproducing of information even if a coupling lens is omitted, especially, an optical disk for optical system realizing recording and reproducing of information for the optical disks of a plurality of kind of which the thickness of protecting layers are different.

This is the optical system for optical disk in which an optical disk of which the numerical aperture of an optical disk side required for recording and/or reproducing of information is 0.60 or more can be used. The system has a light source emitting diverging light , an objective lens converging the diverging light from the light source on the optical disk, a driving means focusing the objective lens and tracking-shifting or changing attitude of the objective lens, the drive means is carried out to configuration performed simultaneously operation changing attitude of the objective lens so that the central axis of the objective lens is faced to the light source direction at the time of tracking-shift.