The three-point bending deformation of a beam under a constant deflection-rate has been analyzed using the constitutive equation of superplasticity. Then the bend test and a tension test of a yttria-stabilized tetragonal ZrO2 polycrystal (Y-TZP) in which the occurrence of superplasticity has been confirmed have been carried out at various deflection-rates and strain-rates at different temperatures. Results of the bend test have been compared with those of the tension test. Outer-fiber stress (σxc)s and strain-rate (εxc)s at the center of the beam have been calculated from measured values of bending force Pc, deflection-rate υc and deflection-rate sensitivity index m' defined as δln Pc/δln υc The strain-rate sensitivity index m obtained from the slope of the log-log plot of (σxc)s and (εxc)s agrees well with the m-value obtained from the tension test within the range of the present experiment. An activation energy of the deformation Q obtained from ln PC1/m' vs. 1/T or ln υC vs. 1/T plot in the bend test corresponds well with the Q-value obtained from the tension test, where T is temperature. A relatively rapid decrease in Young's modulus and an abrupt increase in deflection to fracture with an elevation in temperature are thought to be an indication of the onset of superplasticity. We can conclude from these results that the three-point bend test is a good method to evaluate superplastic properties in ceramics of which tension test is generally not so easy.