A phase synchronization laser device includes: an optical circulator to receive laser light and output return light; an optical splitter to split the laser light into reference and signal light beams; element circuits each including a phase compensator to perform phase control on the split beams of signal light, and output the beams of signal light; optical partial reflection mirrors to allow the reference light or the beams of signal light to enter as beams of incident light, reflect part of the beams of incident light and allow the rest to transmit; and a photoelectric converter to accept and photoelectrically convert the return light, each element circuit performs frequency conversion on an output of the photoelectric converter and detects a phase error of the electrical signal, and each phase compensator compensates for the detected phase error.