With an object of providing an artificial sphincter for which repeated shape changes are possible, and for which the quantity of shape change is sufficient so as to be used as a substitute for a large natural sphincter, an artificial sphincter 11 that opens and closes, as required, either the anus of a living body or part of the intestine 19 led outside the body is provided, wherein this artificial sphincter 11 comprises a pair of shape memory alloy elements 13 that change reversibly between two opposite shapes upon changes in temperature and hinges 15 that link the shape memory alloy elements 1 together in a cylindrical shape.