PURPOSE: To provide high repetition stability with a simple structure comprising the first member having the first/second planes not in parallel and the second member having the first to third protrusions into contact with the first plane and the fourth/fifth protrusions into contact with the second plane, and relatively moving both the members in a ridge line direction formed by the plane.

CONSTITUTION: The first member 1 has a sliding surface constituted of the first/second planes not in parallel, and the second member 2 has three protrusions (not on one straight line) and two protrusions always respectively into contact with the first/second planes, so as to enable the members to slide in a ridge line direction formed by the first/second planes. A position of making drive force act in the second member 2 is ideally a position of negating rotational moment generated in the second member 2 by frictional resistance received by each protrusion at sliding time. In order to bring all the five protrusions of the second member 2 always into contact with the two planes of the first member 1, a contact maintaining mechanism of applying sucking or pressing force to the second member 2 is provided. In this way, a structure is simplified to facilitate manufacture, so as to obtain high repetition stability.