  The $J/\psi$ decay angular distributions have been measured in inelastic
photoproduction in $e p$ collisions with the ZEUS detector at HERA, using an
integrated luminosity of 468 $pb^{-1}$. The range in photon-proton
centre-of-mass energy, $W$, was 50 $< W <$ 180 $GeV$. The $J/\psi$ mesons were
identified through their decay into muon pairs. The polar and azimuthal angles
of the $\mu^+$ were measured in the $J/\psi$ rest frame and compared to
theoretical predictions at leading and next-to-leading order in QCD.
