A fluid machine includes a non-streamline casing capable of forming a stable vortex street on a downstream side by internal and external flows, and an impeller disposed inside the casing. The casing has a vortex generator configured to form the vortex street on the downstream side. The vortex generator is provided with a phase control structure which regulates a phase of a vortex formation that fluctuates along a circumferential direction in a plane including a rear face of the casing and which clarifies a cell structure to be formed along the circumferential direction of the casing to fix, on a surface of the casing, respective positions of cells into a plurality of segmented regions arranged in the circumferential direction. The velocity of the internal flow is increased by the phase control structure.