Properties of oxide layers at the interface between Al metal and YBa2Cu3O7-delta ceramics were investigated using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and impedance measurements. There have been found the oriented grains having their c-plane parallel to the surface of YBa2Cu3O7-delta. When Al metal was evaporated onto the ceramics sample, the aluminum oxide layer was produced at the interface between Al and YBa2Cu3O7-delta because Al metal oxidizes more easily. The oxygen-deficiency was observed at the ceramics side of the interface as examined by X-ray photoelectron spectra. This oxygen-deficiency can be partly replenished by post annealing whereas it can be fully replenished for the sample to which the mechanical polishing is applied beforehand in order to remove the oriented grains. The thickness of aluminum oxide layer was evaluated by means of the impedance measurements using the alternating current three-terminal method.