Disclosed is an optical head apparatus comprising: a light source; a
collimating means of converting a beam of light emitted from the light
source into a substantially parallel beam of light; a focusing means of
focusing the light onto an information medium surface; a beam splitting
means of splitting the beam of light modulated by the information medium;
and a light receiving means of receiving the light modulated by the
information medium, wherein a lens having a negative power and a lens
having a positive power are arranged in this order as viewed from the
collimating means side between the collimating means and the focusing
means, and at least either one of the lenses is moved along an optical
axis to correct spherical aberration occurring on the information medium
surface, and wherein the distance from the lens having the positive power
to the focusing means is set substantially equal to the focal length of
the lens having the positive power.