PURPOSE: To increase pump capacity easily to a high one by forming an annular flow path of liquid metal wound with a coil along the axial direction by coaxially providing a plurality of flow paths differing in the annular diameter.

CONSTITUTION: Within a cylindrical pump casing 11, plural outside cores 13 of the same length are installed at equal spaces and outer coils 15 are wound around a plurality of axially provided slots. An outer duct 12 connected with Na inlet and outlet ports is inserted between the outside cores 13. Within the outer duct 12, an intermediate duct 16 and an inner duct 20 are secured by separators 17, 21 so that a larger annular flow path 19 and a small annular flow path 22 are formed coaxially. An intermediate core 18 is installed within the intermediate duct 16 while inner coils 23 wound around slots of an iron core 24 are arranged axially in the inner duct 20. A prescribed three-phase alternating current is applied to the outer coils 15 and inner coils 23 so that a shifting magnet field is generated between the outside core 13, intermediate core 18 and inside core 24 to make a molten Na flow in the direction of the arrow. In this manner, a pump capacity is increased easily.