Assuming that a display period for one image is one field, a light source turn on period and a light source turn off period are set for the one field. An overall bending displacement period for making bending displacement of all actuator elements is set within the light source turn off period. A gradational display period for performing substantial gradational display and a reset period for resetting the bending displacement of all of the actuator elements are set within the light source turn on period. Subfields of a number corresponding to the maximum gradation level are set within the gradational display period. Timing control is performed so that all row selection is completed within each of the subfields. Accordingly, the gradation level is advantageously extended when a relationship of Tr>>Tf is given between a light-emitting rising time Tr of the picture element and a quenching falling time Tf of the picture element.