An optical pick-up generates a 0-th order diffraction light and .+-.1st
order diffraction lights by a diffraction grating and irradiates the same
to an optical disc. The .+-.1st order diffraction lights have phase
distributions equivalent to a wavefront aberration of the optical disc
when there is a tilt in the optical disc. Distances between the center of
the main optical spot and centers of sub optical spots in a disc radial
direction on a recording surface are whole multiples of a track pitch. The
generation circuit generates a main push-pull signal corresponding to the
0-th order diffraction light and first and second sub push-pull signals
corresponding to the .+-.1st order diffraction lights and generates
tracking error signals TE as differential push-pull signals obtained by
subtracting a sum signal of the first and second sub push-pull signals
from the main push-pull signal.
