  The lighter chargino pair production ($e^+e^- \to \tilde{\chi}^{+}_{1}
\tilde{\chi}^{-}_{1}$) is one of key processes for determination of
supersymmetric parameters at a linear collider. If $\tan\beta$ is a large
value, the lighter stau ($\tilde{\tau}^{\pm}_{1}$) might be lighter than the
$\tilde{\chi}^{\pm}_{1}$, while the other sleptons stay heavier. This case
leads a cascade decay, $\tilde{\chi}^{\pm}_{1} \to \tilde{\tau}^{\pm}_{1}
\nu_{\tau}$ followed by $\tilde{\tau}^{\pm}_{1} \to \tilde{\chi}^{0}_{1}
\tau^{\pm}$, where $\tilde{\chi}^{0}_{1}$ is the lightest supersymmetric
particle. This paper addresses to what extent this cascade decay may affect the
measurements of the chargino mass and its production cross section.
