PURPOSE: To provide large capacity and compactness for a pump by increasing the current in a stator coil.

CONSTITUTION: A plurality of stacked iron core blocks having slots are arranged on the periphery of the outer pipe being provided coaxially, forming an annulus passage for letting conductive fluid flow outside of an inner pipe. Many circular stator coils for letting three-phase AC currents flow for making progressive magnetic fields in the annulus passage are arranged inside the slot of this stacked iron core block, and the stacked iron core block is fixed to a tubular iron core frame, and a stator coil and a stacked iron core block are fastened at large with circular press plates 18 provided at both ends in the axial direction of this iron core frame 17 so as to unit them with the iron core frame 17, and the united object is attached inside the tubular casing 19, and as the material of the stacked iron core block and the iron core frame 17, the one smaller than or practically the same as the outer pipe in thermal expansion coefficient is used.