PURPOSE: To reduce the size of a device for measuring eccentricity of the iron core used with a covered electrode and to detect exactly the rate of eccentricity with said device by disposing magnetic sensors in the direction X and magnetic sensors in the direction Y within the same plane perpendicular to the core wire and driving alternately the same.

CONSTITUTION: A core wire of a welding rod is passed through a guide 2 and is extruded from a die 5; at the same time, a covering material 4 is supplied to the die 5 and is taken out as a covered electrode 10 in the stage of manufacturing the covered electrode. Magnetic sensors 6a, 6b which measure the rate of eccentricity in the direction Y of the core wire of the covered electrode and magnetic sensors 6c, 6d which measure the rate of eccentricity in the direction X are disposed in the outlet of the die 5 within the plane perpendicular to the advancing direction of the core wire. The sensors 6a, 6b and the sensors 6c, 6d are alternately operated at intervals of specified time, by which the magnetic interference of the sensors with each other is obviated and therefore the rate of eccentricity of the core wire is exactly measured without measuring errors. Since the magnetic sensors of both sets are disposed within the same plane, the measuring device itself is made smaller in size.