To facilitate the control of a clearance between the rotor and the stator of a type of pump that fluid is forcibly fed by viscous resistance.

This pump is equipped with a rotor 4 and a stator 3 which is arranged to be positioned near to the rotor 4 and energized in the rotor direction, however, separated from the surface of the rotor 4, a plurality of recessed parts is formed to a surface opposed to the stator 3 or the rotor 4, and also, an introducing port for supplying fluid to respective recessed parts and a discharge port for discharging fluid from respective recessed parts are formed in this pump. Fluid is forcibly fed from the introducing port to the discharge port by viscous resistance of fluid caused by the rotation of the rotor 4 relative to the stator 3 by rotating the rotor 4 centering around its shaft core. A part of force by which the rotor 4 and the stator 3 are mutually energized is supplied by fluid pressure fed back from the pump so that energization force between the rotor 4 and the stator 3 is automatically controlled.