It is made possible to easily obtain a spectacle lens with higher performance in a spectacle lens designing method in which an eyeball motion is taken into consideration. A second low voltage and a second high voltage having a second voltage range between the second low voltage and the second high voltage are divided into a plurality of gamma voltages of a second polarity during a second interval. The cooling system accelerates the fluid to a velocity equal to or greater than the speed of sound in the compressible fluid selected to be used in the system. The interior angle of such a second electrode-side corner is larger than 90\xb0.