PURPOSE: To control the flow of a fluid keeping electrodes always clean by providing a plurality of groups each of which has an electrode in contact with an electrolyte and a means for forming a magnetic field, and turning polarities of the electric fields and magnetic fields selecting them in order.

CONSTITUTION: A plurality of electrodes 2-1∼2-8 are provided intersecting perpendicularly to the moving direction of a fluid in a pass 1 for circulating the electrolyte solution of a fuel cell, and electromagnets 4-1∼4-8 are provided corresponding to the electrodes in the external. The fluid is drived and controlled by actions of the electric fields and magnetic fields, and for example, when an electrode pair of 2-1 and 2-5 is selected with a timer, the perpendicularly intersected magnets 4-3, 4-7 are operated synchronously, and polarities of electric fields and magnetic fields are turned in order. Thus, the process in which an electrode initially being positive becomes negative through several neutral is repeated, electrodes are kept clean always, and the reaction can be continued normally.