The subgap transport in electrostatically gapped bilayer graphene (BLG) is explored by adopting ultrashort constrictions of BLG. We confirmed the emergence of the edge conducting channels, with a residual conductance of $\ensuremath{\sim}2{e}^{2}/h$ per edge of realistic disorder. Transport along the edge state exhibits either Coulomb blockade oscillations or Fabry-Perot interference, depending on the interfacial transparency between the reservoirs and the edge channel. Both residual conductance and band-gap dependence of the penetration range of the edge state from a constriction edge coincide well with the behavior of the theoretically predicted robust edge conducting channel, which forms irrespective of the degree of edge disorder.