To clarify the mechanism of the cochlea, simulations using a mathematical or electrical circuital cochlear model have been performed by many researchers. However, in most of their models, the cochlea was assumed to be straight to simplify their simulations, although the mammalian cochlea is a spiral-shaped duct. A few researchers have already established the spiral cochlear models, but the effects of spiral shape of cochlea are still unclear. In this study, a three-dimensional model of the guinea pig cochlea was established, and numerical simulations were performed using the finite element method (FEM). To examine the effect of the spiral shape of cochlea on its mechanics, the numerical results obtained from the spiral-shaped model were compared with those from the straight model. It was found that the basilar membrane (BM) velocity amplitude and the vibration mode of the BM along the transverse direction in the spiral model were different from those of the straight model.