  We calculate Higgs coupling constants at one-loop level in the Higgs triplet
model (HTM) to compare to future collider experiments. We evaluate the decay
rate of the standard model (SM)-like Higgs boson ($h$) into diphoton.
Renormalized Higgs couplings with the weak gauge bosons $hVV$ ($V=W$\ and\ $Z$)
and the trilinear coupling $hhh$ are also calculated at the one-loop level in
the on-shell scheme. The event rate of the $pp\rightarrow h \rightarrow
\gamma\gamma$ channel in the HTM to the one in the SM can cover the value from
the recent LHC data. We find that in the allowed parameter region by the
current data, deviations in the one-loop corrected $hVV$ and $hhh$ vertices can
be about -1% and +50%, respectively. Magnitudes of these deviations can be
enough significant to compare with the precision future data at the
International Linear Collider.
