PURPOSE: To obtain an electromagnetic flowmeter that has no polarization phenomenon occurring between electrodes and a fluid by alternating the measurement of a voltages induced by the fluid generated between electrodes and the application the measured voltage between electrodes.

CONSTITUTION: Magnetic flux () in the diameter direction of conduit 3 is generated in excited coil 2 by DC current from exciting electric power source circuit 16 and signal voltage Es' induced by the fluid is extracted from a couple of electrodes 5. When change-over switches 7 and 7' are placed at side (a), short-circuit switch 8 is turned off to change the output of electrodes 5 into required signal IO by way of amplifier 9, sampling switch 10, sample holding path 11, averaging circuit 12, and amplifier 13 and when at side (b), short-circuit switch 8 is turned on to change output IO into feedback voltage Ef through feedback circuit 14. Then, it is applied to electrodes 5 and switch circuits 7 and 7', and 8 and 10 are controlled by controlling circuit 15 to discharges charges in fluid 4 formed near electrodes, thereby taking a continuous measurement of a flow velocity while preventing the accumulation of charges.