A novel method for generating quadruple-frequency millimeter-wave (MMW) by using an actively mode-locked fiber ring laser is proposed and demonstrated. In this approach, the optical Mach-Zehnder intensity modulator (MZM) is biased to suppress the odd-order optical sidebands, the fiber laser operates in the second-order rational harmonic mode, and a fiber Bragg grating (FBG) notch filter is used to block the optical carrier. When the MZM is driven by a fixed radio-frequency (RF) source of 10 GHz, a stable MMW signal of 40 GHz with the phase noise better than -76 dBc/Hz at 1-kHz offset is generated.