There is provided a fiber Bragg grating devise comprising an FBG mount that is constituted by sequentially stacking a temperature control plate, a base plate, and a mounting plate, and an SSFBG in which a plurality of FBG units of the same constitution and a plurality of phase modulation portions are alternately formed in the same optical fiber. The temperature control plate is constituted by a thermo module and a heat-insulating member. The base plate is fixed in contact with the upper face of the temperature control plate and the mounting plate is in contact with the upper face of the base plate in a state where the mounting plate is able to glide over the upper face of the base plate. The SSFBG is fixed to contact an FBG contact portion that is established on the upper face of the mounting plate. The phase modulation portions are formed to be capable of expanding and contracting and, as a result of the expansion and contraction of the phase modulation portions, the phase of the carrier wave of the optical pulse signal that is propagated by the phase modulation portions can be changed.