PURPOSE: To easily avoid an obstacle by connecting a plurality of parallel link units constituted of many extending/contracting members, so as to increase redundancy by providing a large degree of freedom and movable range.

CONSTITUTION: Cylinder strokes of respective cylinders 3a to 3c of each parallel link unit 1a to 1d are controlled, to obtain attitudes from an A position to a B position, C position and an arbitrary position. Here in moving from the B position to the C position, a movable base 2d in the point end, left as holding a prescribed attitude, is moved from an arbitrary position while avoiding an obstacle 10. In selecting attitudes even by a single unit of these parallel link units 1a to 1d, a considerable degree of freedom is provided, but by arranging these units in a multiple manner, redundancy is provided to avoid the obstacle 10.