A novel scheme is demonstrated to generate single-sideband optical millimeter-wave signals employing frequency quadrupling. A dual parallel Mach-Zehnder modulator (DPMZM) is used to achieve frequency quadrupling. With electrical phase shifting and bias control, the DPMZM generates optical signal comprised of a carrier and two two-order side-bands. After removing the optical carrier with an optical filter, a quadruple optical millimeter-wave signal is generated. An experimental radio-over-fiber (RoF) transmission system is built. 40 GHz optical millimeter-wave signal with 1 Gb/s pseudorandom bit sequence data is transsmited, whose power penalty is only 0.8 dB over 20 km single-mode fiber (SMF).