Abstract: A fluid machine of an embodiment includes a sealing portion formed of an annular minute gap between a runner band of a runner configuring a rotating portion and a sealing liner which is a stationary portion and arranged in opposition to the runner band. A groove having a quadrangular cross-sectional shape is formed circumferentially on a surface of the sealing liner configuring the sealing portion. In a cross section perpendicular to a groove forming direction of the groove, an angle ?, formed between a side WU of the groove on the most upstream side with respect to the flowing direction of the leakage flow and a side W0 of the groove which is on an extended line of the surface of the sealing liner, is determined to be 15° or more and 40° or less.