OBSERVATION SUBSTRATE, WELL PLATE, SURFACE OBSERVATION DEVICE AND SURFACE OBSERVATION METHOD

PROBLEM TO BE SOLVED: To solve such problems that when an incident light microscope is used, fluorescence is excited not only on a cell surface but inside the cell to act as background light, which results in a low S/N, and that, whereas a confocal laser microscope and a total reflection microscope selectively excite fluorescence present on a specific surface of a cell and give a high resolution image with a high S/N, optical systems are complicated and devices are large and expensive.SOLUTION: An observation substrate for the observation of a sample surface is provided, which includes a body part that is transparent to light at a preliminarily determined wavelength. The body part has a varied surface area where the refractive index is varied at a predetermined pitch on one surface of the body part; the pitch is controlled to be within a ±10% range of an integral multiple of a length obtained by dividing a wavelength in a free space by the effective refractive index in the varied surface area.