A novel technique for the generation of millimeter-wave (mm-wave), i.e., frequency sextupling technique, is theoretically analyzed and experimentally demonstrated. The proposed technique is comprised of two cascaded dual-electrode Mach-Zehnder modulators (MZMs). The first MZM, biased at the minimum transmission, is only used for odd-order optical harmonic generation, and then a second MZM, biased at the maximum transmission, suppresses all odd-order optical harmonics. As an example, a 10 GHz radio frequency (RF) signal, which drives the MZMs, is considered; and a mm-wave signal at 60 GHz, i.e., a frequency sextupler, is obtained. Compared with the conventional techniques without optical band-pass filter, the generated mm-wave signal is robust to fiber chromatic dispersion. The proposed technique is verified by experiments.