To provide an optical pulse period compressing/expanding device and an optical signal generator which require no precise adjustment, cause no degradation in optical signals, variably adjust an optical pulse period arbitrarily and have improved flexibility.

The devices is provided with a chirp light beam generator that generates chirp light beams in which wavelengths are linearly varied from a first prescribed wavelength to a second prescribed wavelength for each prescribed number of pulses of input light beam pulse signals, a wavelength converter which wavelength converts the input light beam pulse signals by the chirp light beams so as to generate wavelength converted optical signals and a chromatic dispersion element which gives propagation delay to the wavelength converted optical signals by chromatic dispersion.