Abstract: The present invention is a film thickness measurement apparatus including a light source, a first optical path, a first condenser lens, a spectrometry unit, a second optical path, a second condenser lens, and a data processing unit. The light source emits measurement light having a predetermined wavelength range. The first optical path guides to an object to be measured the measurement light. The first condenser lens condenses the measurement light. The spectrometry unit obtains a wavelength distribution characteristic of reflectance or transmittance. The second optical path guides to the spectrometry unit the light reflected by or transmitted through the object. The second condenser lens condenses light at an end of the second optical path. The data processing unit analyzes the wavelength distribution characteristic obtained in the spectrometry unit to obtain a film thickness of the object.

Abstract: An observation light generated by an observation-purpose light source has a beam cross section where the light intensity (light quantity) is substantially uniform. A mask portion masks a part of the observation light so that the light intensity of a region corresponding to a reticle image at the beam cross section is substantially zero. The observation light including a shadow region formed corresponding to the reticle image is reflected from a beam splitter and applied to an object to be measured. Based on the contrast (difference between light and dark parts) of a reflected image corresponding to the reticle image projected on the object to be measured, the focus state of the measurement light on the object to be measured is determined.