  We discuss CP asymmetries in $B^0$-meson decays and \BsBs mixing within the
framework of the supersymmetric standard model (SSM). It is shown that \BdBd
and \KK mixings could receive sizable new contributions through box diagrams
mediated by the charginos and charged Higgs bosons. This implies that the
CP-violating phase of the Cabibbo-Kobayashi-Maskawa matrix may have a value
which is different from the one predicted by the standard model (SM). The value
of the CP-violating phase affects the amounts of the CP asymmetries and \BsBs
mixing. We examine predictions for these quantities in both the SSM and the SM,
exploring the difference between the two models.
