1. A measurement apparatus comprising: a dielectric block; a thin film layer which is formed on a face of the dielectric block and brought into contact with a sample, and which has a refractive index lower than that of the dielectric block; a light source for generating a light beam; an incident optical system for causing the light beam to enter the dielectric block so that total reflection conditions are satisfied at the interface between the dielectric block and the thin film layer; a two-dimensional light detection means for measuring the intensity of the light beam totally reflected at the interface at each of a plurality of positions on the cross-section of the beam; and a correction means, wherein a predetermined pattern having a unique shape is formed within a region irradiated with the light beam on the face of the dielectric block, and wherein the correction means is a means for correcting an output from the two-dimensional light detection means, based on the unique shape of the pattern, so that the shape of an object on the face of the dielectric block and the shape of the object, detected by the two-dimensional light detection means, are similar to each other, wherein the correction means matches the output from the two-dimensional light detections means with the unique shape of the pattern as a basis for the correction.