In order to examine the elasto-plastic deformation property of a Ta₂O₅ thin film, a bending experiment is carried out using a micro-cantilever specimen fabricated by means of a focused ion beam. The load-displacement curve shows evident non-linear behavior, and the specimen breaks at P = 478.6 μN. The plastic constitutive equation of the Ta₂O₅ thin film is inversely derived by finite element method (FEM) analyses. It also evaluates the fracture strain of 3.1 × 10^-2. The material properties obtained by indentation include a depth-dependent error due to the loading tip configuration and the deformation constraint by the substrate. The bending test, which has no effect of the deformation constraint, is effective for specifying the mechanical properties of thin films.