  We present a fermionic dark matter model mediated by the hidden gauge boson.
We assume the QED-like hidden sector which consists of a Dirac fermion and
U(1)$_X$ gauge symmetry, and introduce an additional scalar electroweak doublet
field with the U(1)$_X$ charge as a mediator. The hidden U(1)$_X$ symmetry is
spontaneously broken by the electroweak symmetry breaking and there exists a
massive extra neutral gauge boson in this model which is the mediator between
the hidden and visible sectors. Due to the U(1)$_X$ charge, the additional
scalar doublet does not couple to the Standard Model fermions, which leads to
the Higgs sector of type I two Higgs doublet model. The new gauge boson couples
to the Standard Model fermions with couplings proportional to those of the
ordinary $Z$ boson but very suppressed, thus we call it the dark $Z$ boson. We
study the phenomenology of the dark $Z$ boson and the Higgs sector, and show
the hidden fermion can be the dark matter candidate.
