To provide, as a centrifugal pump for transporting an incompressible fluid, a centrifugal pump that is low in manufacturing costs, and can reduce a leakage flow from a discharge side to a suction side through an annular seal and also comprises a wear ring part which hardly generates vibrations.SOLUTION: There is provided a non-contact annular seal which reduces a flow rate of a fluid flowing from a high-pressure side to a low-pressure side of a gap where a rotary body 20 of a rotary machine and a stationary member face each other radially across the gap. This non-contact annular seal is characterized in that: surfaces of the rotary body and stationary member which face each other across the gap smoothly face each other in parallel; and in a cross section parallel with the axial direction, parallel lines AS forming the gap between the rotary body and stationary member and an origin 43 on a high-pressure side of the parallel line, in a cross section of the gap, of at least one of the rotary body and stationary member contain an acute angle.SELECTED DRAWING: Figure 5
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