A rotary machine includes a guide section formed in an annular flow path in communication with a suction volute at an inner circumferential side of the suction volute, at which a plurality of vanes are installed in a circumferential direction, and configured to guide a fluid introduced from the suction volute, and an impeller connected to the guide section in the axial direction and into which the fluid guided by the guide section is introduced. The suction volute has an annular opening section in communication with the guide section at the inner circumferential side, and an inner wall surface extending from the opening section toward the axial direction of the impeller in the axial direction to increase a width dimension in the axial direction and connected to a partition section at an opposite side of the suction nozzle.