The compressors for CO2 refrigerant have a lot of difficulties to achieve high efficiency and reliability because of its very high operating pressure, which causes the deformation for scroll element. The deformations of the fixed scroll during operation fall into the following four categories: (1) pressure deformation due to pressure differences; (2) thermal deformation due to temperature difference; (3) deformation caused by welding for fixing the frame to the shell; and (4) bolt tightening deformation of the compression mechanism. In this study, in order to minimize the deformation during operation, deformations (1) and (2) are grasped by numerical calculations and deformations (3) and (4) are controlled to cancel the deformations (1) and (2) by adjusting the stiffness of fixed scroll. In addition, we measured the deformation under the operation by using the strain gauge in order to confirm that the proper stiffness of fixed scroll can minimize its total amount of deformation.