A laser device comprising: oscillation means for oscillating a laser pulse train (L 0) constituted by a plurality of beams of continuous laser light having frequencies different from each other; demultiplexing means for demultiplexing the laser pulse train oscillated from the oscillation means into a plurality of beams of the continuous laser light (L 1) having frequencies different from each other; amplification means for amplifying each of the beams of the continuous laser light (L 1) demultiplexed by the demultiplexing means; multiplexing means for multiplexing at a predetermined position the beams of the continuous laser light (L 2) amplified by the amplification means, so as to produce multiplexed light (L 3); and phase control means for controlling a phase of each of the beams of the continuous laser light (L 1) such that an output peak of the multiplexed light (L 3) repeatedly appears at the predetermined position at a predetermined time interval; wherein the amplification means includes a pumping light source for oscillating a plurality of beams of pumping light (L p1- L p3) and characterized in that the amplification means further includes a nonlinear crystal for receiving each of the beams of the continuous laser light (L 1) and the plurality of beams of pumping light (L p1- L p3) and configured to make, for one beam of the continuous laser light (L 1), the plurality of beams of the pumping light (L p1 -L p3) incident on the nonlinear crystal such as to satisfy a phase-matching condition of optical parametric amplification, thereby amplifying each of the beams of the continuous laser light (L 1), the nonlinear crystal includes a plurality of nonlinear crystal parts; the amplification means is configured to make one beam of the continuous laser light incident on the nonlinear crystal over a plurality of nonlinear crystal parts and the plurality of beams of the pumping light incident on the nonlinear crystal for each of the nonlinear crystal parts, and each of the nonlinear crystal part is cut at such an angle that the laser light (L 1) and the pumping light (L p) satisfy the phase-matching condition. oscillation means for oscillating a laser pulse train (L 0) constituted by a plurality of beams of continuous laser light having frequencies different from each other; demultiplexing means for demultiplexing the laser pulse train oscillated from the oscillation means into a plurality of beams of the continuous laser light (L 1) having frequencies different from each other; amplification means for amplifying each of the beams of the continuous laser light (L 1) demultiplexed by the demultiplexing means; multiplexing means for multiplexing at a predetermined position the beams of the continuous laser light (L 2) amplified by the amplification means, so as to produce multiplexed light (L 3); and phase control means for controlling a phase of each of the beams of the continuous laser light (L 1) such that an output peak of the multiplexed light (L 3) repeatedly appears at the predetermined position at a predetermined time interval; wherein the amplification means includes a pumping light source for oscillating a plurality of beams of pumping light (L p1- L p3) and characterized in that the amplification means further includes a nonlinear crystal for receiving each of the beams of the continuous laser light (L 1) and the plurality of beams of pumping light (L p1- L p3) and configured to make, for one beam of the continuous laser light (L 1), the plurality of beams of the pumping light (L p1 -L p3) incident on the nonlinear crystal such as to satisfy a phase-matching condition of optical parametric amplification, thereby amplifying each of the beams of the continuous laser light (L 1), the nonlinear crystal includes a plurality of nonlinear crystal parts; the amplification means is configured to make one beam of the continuous laser light incident on the nonlinear crystal over a plurality of nonlinear crystal parts and the plurality of beams of the pumping light incident on the nonlinear crystal for each of the nonlinear crystal parts, and each of the nonlinear crystal part is cut at such an angle that the laser light (L 1) and the pumping light (L p) satisfy the phase-matching condition.