An optical measurement system includes a light source, a spectroscopic detector, a reference sample, a switching mechanism that switches between a first optical path through which a sample to be measured is irradiated with light from the light source and light produced at the sample is guided to the spectroscopic detector and a second optical path through which the reference sample is irradiated with light from the light source and light produced at the reference sample is guided to the spectroscopic detector, and a processing unit that calculates, by performing correction processing based on change between a first detection result at first time and a second detection result at second time, a measurement value of the sample from a third detection result provided from the spectroscopic detector as a result of irradiation of the sample with light from the light source at third time temporally proximate to the second time.