This paper evaluates the effect of geometrical nonlinearity on the buckling load of shear-bending columns. The motivation of this study comes from the recognition that the linear buckling model proposed by Haringx in 1948 seems well fit to the experimental observation in the author's laboratory where high-rise rubber bearings were tested. It, however, contradicts to the numerous test results in the past research both in domestic and overseas as well. As a result of the study in this paper, the geometrical nonlinearity is shown to have a malevolent effect on the post-buckling behavior latent in the low-rise laminated rubber bearings, which are commonly used in a practical design of base-isolated buildings.