PURPOSE: An optical pickup is provided to improve the characteristics of a playback signal by expanding an effective numerical aperture of light reflected and received from an optical disk. CONSTITUTION: An optical path converting device converts a proceeding path of an optical beam emitted from a light source(3). An objective lens(7) focuses the incident optical beam on an optical disk(1). A photo detector(9) receives the optical beam reflected/diffracted from the optical disk. A numerical aperture control member differentiates the effective size of an optical beam passing area according to the proceeding direction of the optical beam. An optical beam shift member(10) shifts at least a part of the reflected optical beam corresponding to the expanded numerical aperture to the inside.
