An observation device comprising: an imaging optical system that forms an image of an observation target contained in a transparent container; a horizontal driving section that moves at least one of the container or the imaging optical system in a horizontal plane; a scanning controller that controls the horizontal driving section to move an observation region of the imaging optical system and to scan the container; a detection section (18,19) that has at least one displacement sensor (18a,18b,19a) detecting a position of the container in a vertical direction, and detects the position of the container in the vertical direction at a position in front of a position of the observation region of the imaging optical system with respect to the container in a movement direction of the observation region; an imaging position adjustment section that adjusts an imaging position of the image of the observation target on the basis of an adjustment value according to the position of the container in the vertical direction, detected by the detection section (18,19); a first temperature measuring section (41a, 41b, 41c) that measures a temperature of a support member (30a, 30b, 30c, 31) that supports the detection section (18,19) as a first temperature; a second temperature measuring section that measures a temperature of a support member (30a, 30b, 30c, 31) that supports the imaging optical system as a second temperature; a third temperature measuring section that measures a temperature of the container as a third temperature; and a correction section that corrects the adjustment value on the basis of a refractive index of the container according to the first temperature, the second temperature, and the third temperature, wherein the imaging position adjustment section adjusts the imaging position of the image of the observation target on the basis of the corrected adjustment value. an imaging optical system that forms an image of an observation target contained in a transparent container; a horizontal driving section that moves at least one of the container or the imaging optical system in a horizontal plane; a scanning controller that controls the horizontal driving section to move an observation region of the imaging optical system and to scan the container; a detection section (18,19) that has at least one displacement sensor (18a,18b,19a) detecting a position of the container in a vertical direction, and detects the position of the container in the vertical direction at a position in front of a position of the observation region of the imaging optical system with respect to the container in a movement direction of the observation region; an imaging position adjustment section that adjusts an imaging position of the image of the observation target on the basis of an adjustment value according to the position of the container in the vertical direction, detected by the detection section (18,19); a first temperature measuring section (41a, 41b, 41c) that measures a temperature of a support member (30a, 30b, 30c, 31) that supports the detection section (18,19) as a first temperature; a second temperature measuring section that measures a temperature of a support member (30a, 30b, 30c, 31) that supports the imaging optical system as a second temperature; a third temperature measuring section that measures a temperature of the container as a third temperature; and a correction section that corrects the adjustment value on the basis of a refractive index of the container according to the first temperature, the second temperature, and the third temperature, wherein the imaging position adjustment section adjusts the imaging position of the image of the observation target on the basis of the corrected adjustment value.