A compatible optical pickup device includes a single light source (50) for emitting light having a wavelength longer than 650 nm, an objective lens (70) formed of a near axis area, a ring type annular lens area, and a far axis area with respect to an apex for focusing light emitted from the light source (50) to form light spots suitable for a first optical disk (40A) which is relatively thin and a second optical disk (40B) which is relatively thick, so as to form a light spot having an FWHM (full width at half maximum) of less than or equal to 0.72 µ m with respect to the first optical disk (40A) and a light spot having an FWHM of greater than or equal to 0.8 µ m with respect to the second optical disk (40B), an optical path changing means arranged on the optical path between the light source and the objective lens for changing a proceeding path of incident light, and a photodetector for receiving light reflected by the optical disk and passing through the objective lens and the optical path changing means and detecting an information signal and/or error signal.