1. A fundus observation device comprising: a first image forming part configured to form a 2-dimensional image of the surface of a fundus oculi of an eye to be examined; a second image forming part configured to form a tomographic image of said fundus oculi; a display part having a first display region and a second display region; a controller configured to cause said display part to display said 2-dimensional image formed by said first image forming part on the first display region, to display said tomographic image formed by said second image forming part on the second display region, and also to display the cross-sectional position information indicating the cross-sectional position of said tomographic image displayed on the second display region, so as to be overlapped with said 2-dimensional image on said first display region; and an operating means, wherein when one point on said 2-dimensional image displayed on said first display region is designated by said operating means, said controller causes said display part to display the designated positional information indicating a position in the tomographic image corresponding to a position inside the eye to be examined indicated by the designated one point, so as to be overlapped with said tomographic image on the second display region.