An objective of the present invention is to provide a measuring device for which the need for adjustment of a coherence optical assembly when changing a molecule to be measured is eliminated. A measuring device (1) comprises: a light source unit (10) which emits a pump beam (PP), a Stokes beam (ST), and a signal beam (SG) a light projection unit (20) which projects the pump beam (PP) and the Stokes beam (ST) upon a subject (S) a light modulation unit (30) which modulates the wavelength of the signal beam (SG) a first light detection unit (50) which detects coherent light between the wavelength-modulated signal beam (SG) and an anti-Stokes beam (AS) from the subject (S) a second light detection unit (52) which detects coherent light between the signal beam (SG) and the wavelength-modulated signal beam (SG) and a signal detection unit (60) which detects, from the signal from the first light detection unit (50), a component which is 90° out of phase with the signal from the second light detection unit (52). An optical parametric oscillator (12) of the light source unit (10) further comprises two nonlinear optical crystals which rotate to incline at the same angle in opposite directions with respect to the optical path.Un objet de la présente invention est de pourvoir à un dispositif de mesure pour lequel est éliminé le besoin dajustement dun ensemble optique de cohérence lors du changement dune molécule à mesurer. Un dispositif (1) de mesure comprend : une unité (10) source de lumière qui émet un faisceau de pompage (PP), un faisceau de Stokes (ST), et un faisceau de signal (SG) une unité (20) de projection de lumière qui projette le faisceau de pompage (PP) et le faisceau de Stokes (ST) sur un sujet (S) une unité (30) de modulation de lumière qui module la longueur donde du faisceau de signal (SG) une première unité (50) de détection de lumière qui détecte une lumière cohérente entre le faisceau de signal (SG) modulé en longueur donde et un faisceau anti-Stokes (AS) e
