  The structure of $\Delta\Delta$ dibaryon is studied in the extended chiral
SU(3) quark model in which vector meson exchanges are included. The effect from
the vector meson fields is very similar to that from the one-gluon exchange
(OGE) interaction. Both in the chiral SU(3) quark model and in the extended
chiral SU(3) quark model, the resultant mass of the $\Delta\Delta$ dibaryon is
lower than the threshold of the $\Delta\Delta$ channel but higher than that of
the $\Delta N\pi$ channel.
