1. A fundus observation device comprising: a first image forming means having an illuminating optical system for emitting illumination light onto fundus oculi of an eye to be examined and a imaging optical system for detecting the illumination light passing through said fundus oculi by the first detecting means, forming a 2-dimensional image of the surface of said fundus oculi based on the detection results by said first detecting means; a second image forming means having a light source which outputs light with a wavelength which is different from said illumination light; an interference optical generating means splitting said light output from said light source into the signal light directed towards said fundus oculi and the reference light directed towards a reference object and generating interference light by overlapping the signal light passing through said flindus oculi and the reference light passing through said reference object; and a second detecting means for detecting said interference light generated, forming tomographic images of said fundus oculi based on the detected results by said second detecting means; an optical path combination and separation means for combining the imaging optical path formed by said imaging optical system and the optical path of a signal light directed toward said fundus oculi and illuminate said signal light onto said fundus oculi through said imaging optical path, as well as separating said imaging optical path from the optical path of the signal light toward said fundus oculi and overlapping said signal light on said reference light by said interference optical generating means; a control means for synchronizing detection timing by said first detection means and detection timing by said second detection means; a correction means for correcting the image positions of said tomographic images based on two-dimensional images based on detection results by said first detection means; and a three-dimensional image formation means for forming three-dimensional images of said fundus oculi based on said tomographic images in which said image positions have been corrected.