  We have analyzed how much the $CP$ angles to be measured at B factories can
deviate from the geometrical ones defined in unitarity triangle under the
existence of new physics. The measurements are given in rephasing invariant
form. If KM matrix is not a $3\times 3$ and unitary matrix, $\tilde\phi_1$ and
$\tilde\phi_3$ is affected, and the value of $\tilde\phi_3$ depends on the
decay mode. The deviation is constrained to be less than the experimental
precision attained in the next decade by the available data of the magnitude of
KM matrix elements. Deviation of the sum of three angles from $\pi$ cannot be
detected unless new physics contributes significantly to $b$ decay or $D$ meson
system.
