The invention discloses an optical measurement device which comprises a measurement device body, a light source, a W-shaped optical fiber and a spectrograph, wherein the W-shaped optical fiber is provided with at least five ports. The optical measurement device is simple to operate, is composed of a vertical incidence measurement device body and an oblique incidence measurement device body, can be used for measuring the film thickness of a three-dimensional structure formed by a single layer film or multiple layers of films, the critical dimension, space appearance and material characteristics, and improves precision of sample measurement. Besides, the vertical incidence part can incline to 54.7 degrees and is used for measuring a monocrystalline silicon solar sample, the oblique incidence part can achieve multi-angle switching, and a friction plate enables the whole switching process to be stable.