The annealing effects of anodized aluminum-based alloys were investigated. Gadolinium and neodymium were employed as respective alloy components and the surface roughness, nanostructure, leakage current and breakdown electric field of these anodized films were investigated as functions of the annealing time. The leakage current was decreased by annealing for 0.5 h at 350 degrees C, but was increased by annealing for 1 h and was decreased again by further annealing. The breakdown electric field and surface roughness showed the same tendency as the leakage current with respect to the annealing time. In the case of the anodized aluminum-gadolinium alloy, annealing for 2 h led to a lower leakage current of 7.4 E-13 A/V, a higher breakdown electric field of 9.9 MV/cm and a lower average roughness of 4.9 nm. The leakage current was studied further by the triangular voltage sweep method. Under a negative bias, the leakage current behaved quite differently from that under a positive bias. In the latter case, it was 1 order of magnitude smaller and could be greatly reduced by annealing for 0.5 h at 350 degrees C. In the former case, however, it was large enough after annealing for 0.5 h and remained after further annealing.