  Recent discovery of neutrino large mixings implies the large mixings in the
diagonalizing matrices of $\bf\bar 5$ fields in $SU(5)$ grand unified theory
(GUT), while the diagonalizing matrices of $\bf 10$ fields of $SU(5)$ are
expected to have small mixings like Cabibbo-Kobayashi-Maskawa matrix. We
calculate the predictions of flavor changing nucleon decays (FCND) in $SU(5)$,
$SO(10)$, and $E_6$ GUT models which have the above features for mixings. We
found that FCND can be the main decay mode especially for GUT with higher rank
unification group. Recent report for $P\rightarrow \pi^0\mu^+$ process implies
$E_6$ or $SO(10)$ GUT if the signal is from the nucleon decay.
