  We investigate the effect of SUSY phases ($\theta_A$ and $\theta_\mu$) on the
$B^0_d - \bar{B}^0_d$ mixing in the minimal supergravity model. It is known
that the complex phase $\theta_A$ $=$ arg($A$) ($A$ is the universal
coefficient of the trilinear scalar couplings) is essentially unconstrained by
the electric dipole moment experiment, while the phase $\theta_\mu$ $=$
arg($\mu$) ($\mu$ is the supersymmetric Higgsino mass) is strongly constrained
to zero. We found that $\theta_A$ does not affect the phase of the $B^0_d -
\bar{B}^0_d$ mixing matrix element $M_{12}(B)$ by numerical analysis of the
renormalization group equations. This means that the measurement of the $B^0_d
- \bar{B}^0_d$ mixing at the future B-factory could give the direct information
on the parameters of the CKM matrix even in the framework of the minimal
supergravity model with the SUSY phase $\theta_A$.
