A measurement apparatus for time-resolved stimulated Raman gain spectroscopic measurement of a measurement sample comprising: a light source unit configured to emit pulsed laser light, used for pump light and Stokes light that excite predetermined molecular vibration of the measurement sample and for probe light that has a same wavelength as the pump light; a first electro-optic modulator for intensity-modulating the probe light with a first reference frequency, and a second electro-optic modulator for intensity-modulating the pump light with a second reference frequency; a pulse control unit configured to cause a time delay of the probe light and then to guide the pump light, the Stokes light, and the time-delayed probe light to the measurement sample; a detection unit configured to detect light transmitted through the measurement sample or light reflected from the measurement sample, comprising: - a first lock-in amplifier configured to perform lock-in detection on a component of the Stokes light modulated with the first reference frequency when the probe light is used with a non-zero time delay, and - a second lock-in amplifier configured to detect a component of the Stokes light modulated with the second reference frequency when the probe light is used with a zero time delay; and an arithmetic processing device comprising a relaxation time computation unit configured to compute the relaxation time of the molecular vibration of the measurement sample based on the time delay amount and the output from the first lock-in amplifier and the second lock-in amplifier. a light source unit configured to emit pulsed laser light, used for pump light and Stokes light that excite predetermined molecular vibration of the measurement sample and for probe light that has a same wavelength as the pump light; a first electro-optic modulator for intensity-modulating the probe light with a first reference frequency, and a second electro-optic modulator for intensity-modulating the pump light with a second reference frequency; a pulse control unit configured to cause a time delay of the probe light and then to guide the pump light, the Stokes light, and the time-delayed probe light to the measurement sample; a detection unit configured to detect light transmitted through the measurement sample or light reflected from the measurement sample, comprising: - a first lock-in amplifier configured to perform lock-in detection on a component of the Stokes light modulated with the first reference frequency when the probe light is used with a non-zero time delay, and - a second lock-in amplifier configured to detect a component of the Stokes light modulated with the second reference frequency when the probe light is used with a zero time delay; and - a first lock-in amplifier configured to perform lock-in detection on a component of the Stokes light modulated with the first reference frequency when the probe light is used with a non-zero time delay, and - a second lock-in amplifier configured to detect a component of the Stokes light modulated with the second reference frequency when the probe light is used with a zero time delay; and an arithmetic processing device comprising a relaxation time computation unit configured to compute the relaxation time of the molecular vibration of the measurement sample based on the time delay amount and the output from the first lock-in amplifier and the second lock-in amplifier.