An optical pickup device is provided which includes a double-wavelength
objective lens (34) that collects a light beam selectively emitted from a
light-emitting/-detecting element (31) that selectively emits a plurality
of light beams different in wavelength from each other, and also return
light from an optical disk (2), a first diffraction grating (45) that
splits the light beam emitted from a light-emitting/-detecting element
(31) into three beams including a zero-order light beam and positive and
negative first-order light beams, a second diffraction grating (46) that
diffracts the return light for traveling along a light path separate from
that of the outgoing light, and a third diffraction grating (47) that
corrects a light-path deviation by diffracting the positive first-order
light beam diffracted by the second diffraction grating (46). The
light-emitting/-detecting element (31) provides a focusing error signal
FE by detecting the negative first-order light beam diffracted by the
third diffraction element (47), and a tracking error signal by detecting
return portions of the positive and negative first-order light beams from
the first diffraction grating (45).