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Long-term photoexcitation experiments were performed on Y Ba 2 Cu 3 O x (x≈6.6) thin films, prepared by pulsed-laser deposition on “tilted” SrTiO3 substrates. From the anisotropic resistance of the samples, the in-plane and the out-of-plane resistivities were calculated. Photoexcitation was carried out with a He-Ne laser at various temperatures from 70 K to 305 K. We observed that the electrical anisotropy ρc/ρab increased at low temperatures, but decreased at high temperatures. This unusual behavior resembles that of the in-plane Hall mobility in a previous study. Possible interpretations according to the models for the photodoping effect in YBa 2 Cu 3 O x are discussed.