  The Wino is an $\mathrm{SU}(2)_{L}$ triplet Majorana fermion and a
well-motivated dark matter candidate. The mass difference between the charged
and the neutral Winos is small thanks to the $\mathrm{SU}(2)_{L}$ symmetry. The
small mass difference makes the charged Wino meta-stable, which provides
disappearing charged track signatures at collider experiments. The constraint
on the Wino dark matter at the LHC strongly depends on the Wino lifetime. We
compute the next-to-leading order (NLO) correction of the charged Wino decay
and make the most precise estimate of the decay rate. We find that the NLO
decay rate is determined by the mass difference and scarcely depend on the Wino
mass itself in the heavy Wino limit. As a result, we find the NLO correction
gives a minor impact on the lifetime of 2-4% increase.
