5G wireless communications use electromagnetic (EM) waves in the 28GHz band, and the EM waves radiated from high-directivity (gain) antennas are hence scattered in a specular direction by walls. If there are obstructions between the transmitting and receiving antennas, the wireless communication quality is deteriorated since the receiver can receive neither direct waves nor reflected waves. In this paper, an EM scattering wall is designed by applying array antenna theory to improve the wireless communication quality. Moreover, the optimum configuration of the EM scattering wall is designed by using the genetic algorithm without a large amount of calculation by an EM simulator.