This invention relates to optical pulse waveform shaping technique intended to combine optical pulses with a low loss and to obtain an optical pulse waveform of an arbitrary intensity distribution by waveform shaping with a low loss. In the present invention, optical pulse waves branched by a beam splitter are caused to reenter the beam splitter with a phase difference between them and are combined with an unbranched optical pulse wave among the beams before branching. Furthermore, the phase difference described above can be variably adjusted. This invention can be utilized as connection means between a laser oscillator and an amplifier having mutually different exciting conditions.
