Phased array antennas whose backscattering level is lower than conventional phased arrays are presented. The array antennas are composed of non-identical elements and plane wave of normal incidence to the array antennas is scattered to non-specular direction. As a result, backscattering level which implies existence of the array antennas is difficult to be detected and secure wireless system is available. The array antennas are named as "Ninja array antennas" because of their secure and invisible performance, where Ninja is Japanese traditional undercover who works stealthily. Beam scanning of the nonidentical array antennas is realized by an excitation making use of array element patterns. Numerical simulation is performed and scattering/radiation performance of the Ninja array antenna using log-periodic dipole array element is demonstrated.