  In a recent paper, Tilma, Everitt {\it et al.} derived a generalized Wigner
function that can characterize both the discrete and continuous variable
states, i.e., hybrid states. As such, one can expect that the negativity of the
generalized Wigner function applied to the hybrid states can reveal their
nonclassicality, in analogy with the well-known Wigner function defined for the
continuous variable states. In this work, we demonstrate that, indeed, the
negativity volume of the generalized Wigner function of the hybrid bipartite
states can be used as an entanglement witness for such states, provided that it
exceeds a certain critical value. In particular, we study hybrid bipartite
qubit-bosonic states and provide a qubit-Schr\"{o}dinger cat state as an
example. Since the detection of the generalized Wigner function of hybrid
bipartite states in phase space can be experimentally simpler than the
tomographic reconstruction of the corresponding density matrix, our results,
therefore, present a convenient tool in the entanglement identification of such
states.
