  When the doubly-charged Higgs bosons $H^{\pm\pm}$ mainly decay into the
same-sign dilepton, a lower bound on the mass is around 400 GeV by the current
LHC data. On the other hand, no such bound has been reported by using the data
at LEP and at the LHC for the case where the same-sign diboson decay
$H^{\pm\pm}\to W^{\pm(*)} W^{\pm(*)}$ is dominant. We study limits on the mass
for such a case by using the current experimental data. From the precise
measurement of the total width of the Z boson at the LEP experiment, the mass
below 43 GeV is excluded with the 95% C.L. It turns out that the results from
four charged lepton searches at LEP do not provide any significant constraint.
We show that a new lower bound is obtained in the diboson decay scenario at the
LHC with the collision energy to be 7 TeV and the integrated luminosity to be
4.7 fb$^{-1}$. By using the data of the same-sign dilepton events, the lower
limit is found to be 60 GeV at the 95% C.L. By the extrapolation of the data to
20 fb$^{-1}$ with the same collision energy, the lower limit is evaluated to be
85 GeV.
