  We consider the minimal seesaw model, the Standard Model extended by two
right-handed neutrinos, for explaining the neutrino masses and mixing angles
measured in oscillation experiments. When one of right-handed neutrinos is
lighter than the electroweak scale, it can give a sizable contribution to
neutrinoless double beta ($0\nu \beta \beta$) decay. We show that the detection
of the $0 \nu \beta \beta$ decay by future experiments gives a significant
implication to the search for such light right-handed neutrino.
