1. A fundus oculi observation device, comprising: a first image forming part configured to optically obtain data and, based on the obtained data, form a fluorescence image of a fundus oculi of an eye administered with a fluorescent agent in advance and a 2D image of a surface of the fluids oculi; a second image forming part configured to optically obtain data and, based on the obtained data, form a tomographic image of the fundus oculi; a display part; and a controller configured to cause the display part to display the 2D image and the fluorescence image formed by the first image forming part side by side with the tomographic image formed by the second image forming part, and to cause the display part to display cross-sectional-position information that represents a relation between a position on the tomographic image and a common position on the 2D image and the fluorescence image.