The Schottky barrier heights (SBH) for α-Al₂O₃(0001)/Ni(111) interfaces have been examined using the first-principles pseudopotential method, and compared with our previous results of Al₂O₃(0001)/Cu(111) interfaces. Configurations with different rigid-body translations parallel to the interface for both the O-terminated and Al-terminated interfaces are examined to clarify the influence of the microscopic interfacial structure on the SBH. The averaged p-type value of the O-terminated interfaces is smaller than that of the Al-terminated interfaces, similar to the Al₂O₃/Cu interfaces, although the variation within each type of interface stoichiometry is also substantial. This indicates that the SBH depends on both the interface stoichiometry and the configuration, in contradiction with the conventional models, which can be explained by the different interface dipole associated with the charge transfer and configuration of each interface.