To shorten the time required by eliminating useless motion of an arm at the time of changing a work.

First and second arms 2, 3 rotationally driven around a common shaft within flat surfaces parallel with each other by driving sources different from each other are provided, work support bases 5 are connected to other end parts of a pair of driven arms 2d, 3d one ends of which are respectively connected to one head end parts of both of the arms 2, 3 free to rotate, a work support base 6 is connected to the other end parts of a pair of driven arms 2e, 3e one ends of which are respectively connected to the other head end parts of both arms 3 free to rotate, and the driven arms 2d, 3d, 2e, 3e are respectively connected to the first and second arms 2, 3 so that both of the work support bases 5, 6 are arranged on the same side to each other with the shaft as their standard.