Abstract: A measurement device includes a light emitter, a light receiver, and a computation processor. The light emitter irradiates, with light, a fluid of an irradiation target. The light receiver receives coherent light scattered by the irradiation target and outputs a signal corresponding to an intensity of the coherent light. The computation processor generates a frequency spectrum for a temporal change in a signal strength and calculates, based on the frequency spectrum, a calculation value for a flow state of the fluid flowing in the irradiation target. The computation processor generates a first frequency spectrum with the fluid in a first flow state, generates a second frequency spectrum with the fluid in a second flow state in which the fluid has a flow rate lower than in the first flow state, and calculates a usable frequency range based on a comparison between the first frequency spectrum and the second frequency spectrum.