To allow more accurate and more appropriate observation of a biological sample when observing the biological sample using inspection light, by allowing the considerable increase in intensity of evanescent light generated by the inspection light even in the case that the inspection light has such an irradiation intensity that the biological sample is not adversely affected.

An observation device 100 for use in observation of a sample 20 being a biological sample includes a light source unit 104 and an optical member 102 which is provided between the light source unit 104 and the sample 20 and emits inspection light generated by the light source unit 104 toward the sample 20. The sample 20 is placed in a position 306 being a prescribed position on a total reflection surface, and the optical member 102 irradiates the sample in a first direction in which the inspection light is totally reflected in the position 306, and totally reflects therein the inspection light totally reflected in the position 306, in a second direction being different from the first direction and being a direction in which the inspection light is to be totally reflected in the position 306, to further irradiate the sample in the position 306 with the inspection light in the second direction.