  We discuss direct CP violation in three-body decays of $B$ meson such as
$B^\pm \to K^\pm\pi^+\pi^-$, which involves various intermediate resonance
states, such as $B^\pm \to K^*_i \pi^\pm$ and $B^\pm \to \rho K^\pm$, where
$K^*_i$ represents the $\pi K$ resonance. Due to the large final state
interaction phases of the resonances, the CP asymmetry can be as large as the
25% level near the kinematical region where the $K^*_i$ and $\rho$ resonances
overlap. By examining a Dalitz plot of this mode and combining a measurement of
the branching ratio for $B^\pm \to \rho^\pm K$, it is possible to extract the
weak phase, $\phi_3$= arg$(-V_{ud}V_{ub}^*/(V_{cd}V_{cb}^*))$, of the
Kobayashi-Maskawa matrix.
