  We propose a new method to extract the CKM phase angle \gamma (\equiv \phi_3)
from the isospin analysis in B \to K \pi decays. Unlike previously proposed
methods, we do not employ flavor SU(3) symmetry, so that this method is free
from the hadronic uncertainty coming from the SU(3) breaking effect. Neither we
adopt any Dalitz-plot analysis, which may involve multiple strong phases and
large final state interactions. After including small CP violating terms in B^+
\to K^0 \pi^+ and color-suppressed electroweak penguin contribution in B^0 \to
K^+ \pi^-, whose values are estimated from the QCD factorization, we obtain
\gamma = ({70}^{+5 +1 +2}_{-14 -1 -3})^\circ \textrm{or} {106^\circ}< \gamma <
{180^\circ}. The first error is due to the experimental errors mainly caused by
mixing-induced CP asymmetry S_{{K_s} \pi^0}. The second and third errors come
from the theoretical uncertainty for two above-mentioned small contributions,
respectively. Since we utilize only the isospin relations in B \to K \pi
decays, this method will work well, regardless of possible new physics effects
unless the isospin relations do not hold.
