  We reexamine a renormalizable model of a fermionic dark matter with a gauge
singlet Dirac fermion and a real singlet scalar which can ameliorate the scalar
mass hierarchy problem of the Standard Model (SM). Our model setup is the
minimal extension of the SM for which a realistic dark matter (DM) candidate is
provided and the cancellation of one-loop quadratic divergence to the scalar
masses can be achieved by the Veltman condition (VC) simultaneously. This model
extension, although renormalizable, can be considered as an effective
low-energy theory valid up to cut-off energies about 10 TeV. We calculate the
one-loop quadratic divergence contributions of the new scalar and fermionic DM
singlets, and constrain the model parameters using the VC and the perturbative
unitarity conditions. Taking into account the invisible Higgs decay
measurement, we show the allowed region of new physics parameters satisfying
the recent measurement of relic abundance. With the obtained parameter set, we
predict the elastic scattering cross section of the new singlet fermion into
target nuclei for a direct detection of the dark matter. We also perform the
full analysis with arbitrary set of parameters without the VC as a comparison,
and discuss the implication of the constraints by the VC in detail.
