Magnetostatic interaction of magnetic domain walls (DWs) is investigated by using magnetic force microscopy (MFM) at the remanent state in closely placed Co dual rings. The Co dual rings are 10 and 20 nm in thickness and the spacing between them is varied. In an array of dual rings varying in steps of 10 degrees against the direction of an applied field, the angular dependence of DW interaction shows an obvious change from coupling to decoupling of the DWs in the MFM measurements. It is found that the strong interaction between DWs at smaller angles and smaller spacing is owed to the surface magnetic charge attraction. On the other hand, monopole-like magnetic charge attraction is related with weak DW interaction at higher angles and a larger spacing. In addition, the dependence of the Co thickness on the magnetostatic DW interaction can be explained by the volume magnetic effects. (C) 2016 Elsevier B.V. All rights reserved.