  We present analytic results for one-loop radiative corrections to off-shell
decay $H^* \rightarrow W^+W^-$ in 't Hooft-Veltman gauge within Standard Model
framework. In numerical results, we show off-shell decay rate and its
corrections with varying off-shell Higgs mass. The results show that the
corrections are of $10\%$ contributions to total decay rates. Furthermore, we
study the impacts of one-loop radiative corrections to off-shell decay $H^*
\rightarrow W^+W^-$ in Higgs processes at future colliders. The signal
processes such as $e^-e^+\rightarrow ZH^*\rightarrow Z(WW)$ with including the
initial beam polarizations and $e^-e^+\rightarrow \nu_e\bar{\nu}_e H^*
\rightarrow \nu_e\bar{\nu}_e (WW)$ and $e^-\gamma \rightarrow e^-H^*
\rightarrow e^-WW$ are examined. We find that the effects are visible impacts
and these should be taken into account at future colliders.
