  We calculate the effective mass m_\omega^* of the \omega-meson in nuclear
medium by the \sigma-\omega model with a vector field self-interaction (VFSI).
We found that the direct and the indirect effects of the VFSI almost cancel
each other and the result is changed only slightly at the normal density. The
VFSI makes m^*_\omega smaller at lower density and makes m_\omega^* larger at
higher density. However, both effects are not large.
