An output member is connected with an input member through three sets of link mechanisms for alteration in attitude. The link mechanism includes end portion link mechanisms on an input side and an output side, respectively, and an intermediate link member. The link mechanism is such that a geometric model of each of the link members expressed by lines represents such a shape as an input side portion and an output side portion relative to a center of the intermediate link member are symmetrical with each other. By actuating two or more sets of the link mechanisms by means of a link mechanism drive source, the attitude of the output member is controlled. Through the inside of an arrangement of the link mechanisms, a flexible wire is provided for transmitting a rotational force in a direction of arrangement of the input and output members.