  We propose an extended Nambu--Jona-Lasinio model to include the heavy mesons
with the heavy quark symmetry. The quark current-current interaction is
generalized to include the heavy quark currents. In order to comply with the
heavy quark spin symmetry at the heavy quark limit, the quark mass dependence
of the interaction strength is introduced. The light and heavy pseudo-scalar
and vector meson, their masses and the weak decay constants, are calculated in
the unified frame.
