  Using a phenomenological model with vector-type interactions, we discuss a
role of repulsive force in the quark-hadron phase transition at high density.
For realization of the quark phase at high density, strong vector coupling is
needed in the hadron phase, while it is forbidden in the quark phase. For the
quark-phase, a NJL-type model with a multi-quark interaction is investigated.
We show that, in this model, the restoration of chiral symmetry decreases
effective vector coupling and the quark phase is realized at high density, even
if we have strong vector coupling at low density. In this model, the strong
coupling in the hadron phase is induced by the chiral symmetry breaking.
