To allow the user to easily wash an electrode section without replacement of a process flow medium and without removing a measurement pipe.

The electromagnetic flowmeter where a flow of a flow medium 2 is electrically measured by applying an alternate magnetic field 5 to the conductive flow medium 2 flowing in a measurement pipe 2 almost at a right angle to the flowing direction of the flow medium 2 and detecting an electromotive force induced in the flow medium 2 by means of a couple of electrodes 6 is provided with a voltage application means 8 applying a DC voltage to a couple of the electrodes 6. In the case of washing the electrodes 6, the voltage application means 8 is used to apply a voltage to a couple of the electrodes 6 to supply a current to the flow medium 2 between the electrodes 6 in a state that the flow medium 2 is filled in the measurement tube 1 at least at a level till the flow medium 2 is in contact with a couple of the electrodes 6 and the alternate magnetic field 5 is applied to the flow medium 2.