This report presents the mechanism and unique features of hysteresis in bending electrostriction of polyurethane films. The films were made of segmented polyester-polyurethanes and coated with a thin gold electrode on both surfaces. The application of a 2-MV/m electric field to the 0.2-mm-thick film caused a bending deformation, which showed hysteresis. The hysteresis was closely related to the absorption current, suggesting that its origin is ionic polarization attributed to ionic impurities in the polyurethane. The existence of ionic polarization after the removal of the electric field was shown by measuring a thermally stimulated discharge current. In addition, a couple of unique features of the hysteresis in the bending deformation are described. One of the features is that the prior application of an electric field significantly improves the bending speed in the successive application. The other is that the prior application also controls the bending direction in the subsequent application of an electric field of opposite polarity.