A centrifugal fluid machine includes a rotor, a low pressure compression unit provided on one side in the axial direction of the rotor, a high pressure compression unit provided on the other side in the axial direction of the rotor, a partition wall 13 that separates the low and high pressure compression units, and a high pressure-side discharge passage 54 formed on the side of the high pressure compression unit of the partition wall 13, extending in the radial direction of the rotor, and provided along the partition wall 13, wherein the partition wall 13 has a wall body 71, a passage deformation suppression member 72 that is provided between the wall body 71 and the high pressure-side discharge passage 54 and can deform the high pressure-side discharge passage 54, and an biasing mechanism 73 that is provided between the wall body 71 and the passage deformation suppression member 72.