  The CCD magnitudes in Johnson $BV$ and Cousins $R$ photometric passbands are
determined for the optical transient of GRB 990123. These observations have
been taken approximately 12 hours after trigger of the gamma-ray burst. BVR
photometric light curves are obtained by combining the published data with the
present measurements. They indicate that the flux decay constants in $BV$ and
$R$ passbands are almost the same. Its value is $1.1\pm 0.06$. Such decay is
quite consistent with the fireball models for the optical transient.
