  We propose a new mechanism where both Dirac masses for the charged-leptons
and Majorana masses for neutrinos are generated via quantum levels. The
charged-lepton masses are given by the vacuum expectation values (VEVs) of the
Higgs doublet field and that of a triplet field. On the other hand, neutrino
masses are generated by two VEVs of triplet Higgs fields. As a result, the
hierarchy between the masses for charged-leptons and neutrinos can be explained
by the triplet VEVs which have to be much smaller than the doublet VEV due to
the constraint from the electroweak rho parameter. We construct a concrete
model to realize this mechanism with discrete $\mathbb{Z}_2$ and $\mathbb{Z}_4$
symmetries, in which masses for neutrinos and those for the muon and electron
are generated at the one-loop level. As a bonus in our model, the deviation in
the measured muon $g-2$ from the standard model prediction can be explained by
contributions of extra particle loops. Besides, the lightest $\mathbb{Z}_2$-odd
neutral particle can be a dark matter candidate. The collider phenomenology is
also discussed, especially focusing on doubly-charged scalar bosons which are
necessary to introduce to occur our mechanism.
