To provide a measuring device capable of suppressing reuse of a spent device for measurement.

This measuring device is equipped with a measuring device mounting part for mounting a measuring device having a cavity for holding a sample including a test material, a sample sucking means for sucking the sample into the cavity of the measuring device mounted on the measuring device mounting part, a light source for emitting light entering the cavity, a photodetector for receiving light emitted from the cavity, an operation part for outputting the concentration of the test material included in the sample based on the light receiving quantity by the photodetector, and a light transmittance changing means for applying processing for lowering a light transmittance of the surface of the measuring device relative to the surface of the measuring device mounted on the measuring device mounting part.