A laser device including a plurality of oscillating means for oscillating a plurality of laser lights being continuous lights and having frequencies different from each other, respectively, multiplexing means for multiplexing, after amplifying or without amplifying, the respective laser lights oscillated from the respective oscillating means at a predetermined position to generate a multiplexed light, and phase control means for controlling the phase of each of the laser lights so that a peak in output of the multiplexed light repeatedly appears at predetermined time intervals at the predetermined position (so that the same pulse temporal waveform repeatedly appears at predetermined time intervals).