Geomagnetic activity asymmetry in the northern and southern hemispheres is studied. It is shown, that the higher is the level of magnetic activity the greater is asymmetry. It is found, that the asymmetry of hemispheres shows itself in the 06–18-hourly component of magnetic activity daily variation, while the asymmetry in the 00–12-hourly component is completely absent. The cause of geomagnetic north-south asymmetry is supposed to be Pedersen meridional current between high and low latitudes in the ionosphere. The qualitative model of formation of asymmetry connected with the solar wind electric field is proposed.