To make a forward/reverse turning angle by a cylinder device 180° or more in a turning unit.

Between a turning body 1 and a fixed part 3, a main cylinder device 10 is arranged and between the fixed part 3 and the main cylinder device 10, a subcylinder device 20 is arranged. By extending/contracting movement of the subcylinder device 20, swivel force is given to the main cylinder device 10, so as to control in a turn direction, in this condition, by extending/ contraction movement of the main cylinder device 10, turn force is given to the turn unit 1, so that the turning body 1 can be right/left turned at a large turn angle of 180 degrees or more.