To enable the swinging of a first and a second rigid surface highly precisely keeping in parallel without any play and friction load in every link by forming an elastic fulcrum mechanism with an elastic member and making each of upper/lower ends for connecting upper and lower rigid surfaces an elastic fulcrum.

An upper rigid surface 3 is capable of swinging laterally keeping parallel with a lower rigid surface 4 as a base surface of a fixed position. That is, the upper rigid surface 3 is connected to upper ends of rigid parts 5, 6 through each elastic part 1 of the function of the elastic fulcrum. The lower ends of rigid parts 5, 6 are connected to the lower rigid surface 4 through each elastic part 2 of the function of the elastic fulcrum. The rigid surface 3, 4 is folded in the right angle along each of left and right edge and rigid parts 5, 6 are also folded in right angle along the inner side surface to enhance rigidity. A parallelogrammatic link mechanism is thus formed only by a pressed and folded plate.