A measurement apparatus includes a dielectric block, a thin film layer formed on the dielectric block and brought into contact with a sample, a light source for generating a light beam, an optical incident system for causing the light beam to enter the dielectric block so that the light beam is totally reflected at the interface between the dielectric block and the thin film, and a two-dimensional light detection means for detecting the intensity of the light beam totally reflected at the interface. A predetermined pattern is formed within a region irradiated with the light beam on the dielectric block. The measurement apparatus includes a correction means for correcting an output from the two-dimensional light detection means, based on the pattern, so that an object on the face of the dielectric block is similar to the object detected by the two-dimensional detection means.