The invention relates to wavelength measurement techniques, in particular to a precision laser wavelength measurement device and a precision laser wavelength measurement method. The precision laser wavelength measurement device comprises a femtosecond pulse laser, a PPLN (periodically poled lithium niobate) crystal, photonic crystal fibers, a first convex lens, a first attenuator, a first half-wave plate, a diaphragm, a second attenuator, a second half-wave plate, a first polarization beam splitter, a third half-wave plate and a second polarization beam splitter. The PPLN crystal, the photonic crystal fibers, the first convex lens, the first attenuator and the first half-wave plate are sequentially positioned on an emergent light path of the femtosecond pulse laser; the diaphragm, the second attenuator, the second half-wave plate, the first polarization beam splitter, the third half-wave plate and the second polarization beam splitter are sequentially positioned on a to-be-measured laser path. An emergent light path of the second polarization beam splitter is provided with a reflection grating, and a second convex lens, an optical filter, a third convex lens, a third attenuator and an avalanche diode detector are sequentially arranged on a reflection light path of the reflection grating; a spectrometer is connected to a signal output end of the avalanche diode detector. The precision laser wavelength measurement device and the precision laser wavelength measurement method have the advantages of simple structure, simplicity and convenience in operation, easiness in adjustment, low external disturbance, high stability and extremely high precision.