To realize an optical limiter function which operates at a high speed, employing a simple constitution.

Incident light beams (a wavelength λs) of an optical input port 10 are inputted into a port A of an optical circulator 12. Signal light beams (a wavelength λs) outputted from a port B of the circulator 12 are made incident on an end face 14a of an electric absorbing type optical modulator 14. A laser light source 16 generates CW light beams having a wavelength λp which is made different with respect to the wavelength λs of the signal light beams. The output light beams of the source 16 are made incident on another end face 14b of the modulator 14. The modulator 14 converts the signals having the wavelength λs into light beams having a wavelength λp with matched pulse peaks and the beams are outputted toward the port B of the circulator 12 from the end face 14a. The circulator 12 supplies the optical pulse having the wavelength λp outputted from the modulator 14 to a saturable absorber 18 from a port C. The absorber 18 improves the quenching ratio of the inputted light beams and outputs the light beams to the external from an output light port 20.