PURPOSE: To make an oxide film hardly formable on a molten metal and to simplify the construction of a piping by disposing a driving stator to an in-pump duct of an electromagnetic pump, providing a control stator to a flow passage for the molten metal and providing an opening means to restore the atm. pressure in the supply duct.

CONSTITUTION: The molten metal (a) introduced into the in-pump duct 13 receives the thrust and the supply of the molten metal is started when currents of successively shifted phases are passed to the driving stator 16 to generate an upward moving magnetic field in the duct 13. The supply of the molten metal (a) can be continued even if the stator 16 is stopped as far as there is a head (h) of the molten metal surface between a supplying point 12 and a supplying point 15. The stator 16 is stopped and a stator 17 is started to form the moving magnetic field in the direction opposite from the flow direction of the molten metal (a) and to apply the braking power enough to overcome the flow to the molten metal in the case of stopping the supply. The molten metal (a) in the duct 14 is thereby stopped. The output of the stator 16 is decreased and is maintained at the output enough to offset the gravity acting on the molten metal by the head (h).