  The homogeneity of the cosmic microwave background radiation (CBR) is one of
the most severe constraint for theories of the structure formation in the
universe. We investigated the effect of the gravitational scattering (lensing)
of galaxies, clusters of galaxies, and superclusters on the anisotropy of the
CBR by numerical simulations. Although this effect was thought to be
unimportant, we found that the gravitational scatterings by superclusters can
significantly reduce the anisotropy of the CBR. We took into account the
exponential growth of the distance between two rays due to multiple
scatterings. The bending angle of each ray grows through the random walk
process. On the other hand, difference between two rays grows exponentially
while it is small. This exponential growth is caused by coherent scatterings
that two rays suffer, and was neglected in the previous studies. The
gravitational scattering by superclusters reduces the observed temperature
anisotropy of the CBR at present time approximately by 40--60 $\%$ from that at
the recombination time for angular scale up to a few degrees if the
supercluster were formed at $z=$2--4.
