A three-dimensional measurement device includes an optical system that: splits an incident light into two lights; radiates one light to a measurement object and the other light to a reference surface; and emits the combined light; a first irradiator that emits a first light that comprises a polarized light of a first wavelength and enters a first element of the optical system; a second irradiator that emits a second light that comprises a polarized light of a second wavelength and enters a second element of the optical system; a first camera that takes an image of the first light emitted from the second element when the first light enters the first element; a second camera that takes an image of the second light emitted from the first element when the second light enters the second element; and an image processor that performs measurement based on the images.