PURPOSE: To obtain a bearing device of a movable impeller with a long bearing life by dividing the bearing of a variable impeller shaft into a radial bearing and a thrust bearing and fitting the thrust bearing finely adjustably.

CONSTITUTION: A thrust bearing 40B is connected to a screw provided at the end of a radial bearing 40A, and in case this thrust bearing 40B is abraded and an impeller 8 is pushed out to a casing liner 11 (not shown in the figure) by a centrifugal force when a pump is in operation and the gap between the impeller 8 and casing liner 11 becomes an allowable value or less, a fixing tool 42 fixing the thrust bearing 40B is removed, the thrust bearing 40B is pushed out to an arm 19 side with a screw, a shim 41 with a predetermined thickness is inserted, and the fixing tool 42 is again fitted to fix them. Thereby, no replacement of the bearing is required and the life of the bearing can be extended.