An element in which only a single domain-wall can move sidewise, having a crystal plate of an irregular ferroelectric which is Z-plated at opposite surfaces and is then cut or cleaved in the direction at its periphery and transparent electrodes for the polarization reversal provided at the central portions of the opposite Z-planes. The element includes at least a domain configuration such that two nucleus regions of opposite polarities are disposed on opposite sides of the region where the electrodes are provided.