A stabilized optical pulse generator using RHML-FRL is provided. The stabilized optical pulse generator comprises an optical fiber ring composed of optical fibers, an optical amplifier and a modulator for optical modulation, an electric signal generator generating high frequency signals and an optical pulse stabilizer. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. Wherein, for a resonance frequency of the optical fibers of fc, the modulating frequency applying to the modulator is detuned from the electric signal of the frequency of fm by frequency of the resonance frequency fc divided by integer of p. Optical pulse trains of repeating frequency of p times of fm+fc/p or fm−fc/p are generated. The optical pulse trains are stabilized by suppressing carrier components and a part of high frequency components as well as suppressing the random oscillations of the cavity resonance modes and intermediate longitudinal modes with respect to the main longitudinal modes which are frequency spaced that is equal to the repetition frequency of the generated optical pulse trains.