  We discuss the 750 GeV diphoton excess at the LHC@13TeV in the framework of
leptophobic U(1)$^\prime$ model inspired by $E_6$ grand unified theory (GUT).
In this model, the Standard Model (SM) chiral fermions carry charges under
extra U(1)$^\prime$ gauge symmetry which is spontaneously broken by a
U(1)$^\prime$-charged singlet scalar ($\Phi$). In addition, extra quarks and
leptons are introduced to achieve the anomaly-free conditions, which is a
natural consequence of the assumed $E_6$ GUT. These new fermions are vectorlike
under the SM gauge group but chiral under new U(1)$^\prime$, and their masses
come entirely from the nonzero vacuum expectation value of $\Phi$ through the
Yukawa interactions. Then, the CP-even scalar $h_\Phi$ from $\Phi$ can be
produced at the LHC by the gluon fusion and decay to the diphoton via the
one-loop diagram involving the extra quarks and leptons, and can be identified
as the origin of diphoton excess at 750 GeV. In this model, $h_\Phi$ can decay
into a pair of dark matter particles as well as a pair of scalar bosons,
thereby a few tens of the decay width may be possible.
