To provide an optical signal processing apparatus with a sufficiently simplified circuit configuration to a degree of being practically available that converts an optical signal resulting from multiplexing a plurality of unsynchronized optical signals whose wavelengths differ from each other into an optical signal resulting from multiplexing a plurality of synchronized optical signals whose wavelengths differ from each other so as to attain multi-wavelength simultaneous processing.

The optical signal processing apparatus is provided with an optical signal synchronizing unit 10 including: a wavelength demultiplexer 11 that demultiplexes a WDM signal resulting from multiplexing n-waves of unsynchronized optical signals by each wavelength; an n×m optical switch 12; m delay circuits; an optical delay unit 13 for synchronizing timings of optical signals outputted from the optical switch 12; a multiplexer 14 for multiplexing n-waves of optical signals whose timings are synchronized and outputted from the optical delay unit 13; and a waveform shaping unit 15 for shaping the waveform of the WDM signal outputted from the multiplexer 14.