A quantitative, high-sensitivity examination of defects in a transparent product is realized, using a low-cost and space-saving optical dimension measuring apparatus to carry out measurement in a non-contact manner to avoid damaging the object of inspection and to avoid sensory examination. A transparent body to be examined is disposed between a light emitting unit and a light-receiving unit arranged opposite each other. A change in an optical path caused by a defect in the transparent body is detected based on a change in a light ray emitted from the light emitting unit and being incident on the light-receiving unit after passing through the transparent body and a light-blocking object disposed between the transparent body and the light-receiving unit.