The present invention is an optical clock signal extraction device, comprising first conversion means and second conversion means for enabling to extract an optical clock signal without depending on the polarization direction of an input optical signal. The first conversion means comprises a first optical converter and a continuous wave light source of which wavelength is λ2, where an input optical signal of which wavelength is λ1 and continuous wave light of which wavelength is λ2 are input to the first optical converter, and an intermediate optical signal of which wavelength is λ2 is generated and output without depending on the polarization direction of the input optical signal. The second conversion means has a second optical converter, where the intermediate optical signal is input to the second optical converter, and an optical clock signal of which wavelength is λ3 is generated and output by the passive mode locking operation of the second optical converter. The input optical signal is input from the end face L1 of the first optical converter, and the continuous wave light of which wavelength is λ2 is input to the first optical converter from the other end face of the first optical converter. The intermediate optical signal is output from the end face of the first optical converter and input to the end face of the second optical converter. The optical clock signal is output from the other end face of the second optical converter.