  We report the updated UV luminosity function (LF) of Lyman break galaxies
(LBGs) at z~5. Combining with lower redshift data, we found that the evolution
of UV LF is differential depending on the UV luminosity; i.e., the number
density of luminous LBGs does not change significantly from z=5 to 3, while the
number density of faint (L<L*) galaxies increases by a factor of five. We also
found the signs of differential evolution within other observational results
for LBGs at z~5. UV-luminous objects show strong clustering, and they have weak
or no Lyman-alpha emissions while showing prominent metal absorption lines.
There is also a clear deficiency of objects with blue UV-optical colors for
those bright in rest-frame optical bands (from the Spitzer/IRAC data obtained
by the GOODS project). By the SED fitting using rest-frame optical to
near-infrared photometry data it is suggested that most luminous objects at z~5
have already accumulated stellar mass more than 10^10 Msun. We discuss that
this differential evolution might be understood as a consequence of the biased
galaxy evolution.
