To effectively inhibit contact of an impeller and a casing in a pump having a depressed grooves generating lift formed on the impeller and/or the casing.

This pump 10 is provided with a roughly disk shape impeller 36 and a casing 39 rotatably storing the impeller 36, sucks fluid to pump channels 44, 46 in the casing 39 and raises pressure thereof by rotation of the impeller 36, and delivers the fluid out of the casing 39. The depressed groove 36c sealed from the pump channels 44, 46 is formed on at least either the surface of the impeller 36 in a suction side or the casing inner surface 40b in the suction side opposing to the surface of the impeller 36, but no depressed groove sealed from the pump channels 44, 46 is formed on a surface of the impeller 36 in a delivery side and a casing inner surface 38b in the delivery side opposing to the surface of the impeller 36.

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