PURPOSE: To reduce manufacturing cost by providing a fitting-in hole in which one end of an operation lever fulcrum shaft is fitted and a member for preventing coming-off which prevents coming-off of the operation lever support point shaft from the fitting-in hole in a transmission case.

CONSTITUTION: A fitting-in lateral hole 31 in which an operation fulcrum shaft 30 can be fitted freely from a side is formed in a front part and on a side of a cylinder case 5d, and one end of the operation lever fulcrum shaft 30 is fitted in the fitting-in lateral hole 31. Moreover, a member 33 for preventing coming-off which is locked in a locking portion 32 formed in a section which is exposed from the fitting-in lateral hole 31 of the operation lever fulcrum shaft 30 and prevents coming-off of the operation lever fulcrum shaft 30 from the fitting-in lateral hole 31 is mounted in the front part and on the side of the cylinder case 5d by bolts. Consequently, it is possible to omit a welding process and a process in which welding distortion is removed. In addition, operation levers R1 R3 do not bend easily, and it is possible to increase the strength in supporting the operation levers R1 R3. Consequently, it is possible to reduce manufacturing cost and obtain a fixing structure which excels in durability.