PURPOSE: To permit to work the internal wall surface of the scroll into a predetermined dimension and improve the sealing property upon meshing as well as the performance of the scroll by a method wherein the outer peripheral end of the scroll body is worked under a condition that the outer peripheral end is extended to an extent longer than the same end upon finishing and the extended section is cut off after finishing the working of internal wall surface.

CONSTITUTION: The outer peripheral end 80 of the scroll body 282, 302 is extended than the same end 41 upon finishing the working thereof. Under this condition, the internal wall surface 50 is cut sequentially from the internal wall surface 50 of the outer peripheral end 41 toward the center of the scroll by a cutting tool such as a mill cutter or the like, thereafter, the outer wall surface 60 is cut. Then, unnecessary section of the extended section 80 is cut off by an end mill cutter or the like to obtain a predetermined finishing dimension. Thus, the internal wall surface 50 is worked under a condition that the rigidity of the outer peripheral end 41 upon finishing is reinforced, therefore, the tilting of the upper part of outer peripheral end 41 may be reduced and the upper part of internal wall surface 50 of the same peripheral end 41 may be worked into the predetermined finishing dimension. Accordingly, the sealing property upon meshing of the scroll members 28, 30 may be improved and the performance of the hydraulic machine may be improved.