In the optical structure observation apparatus according to an aspect of the present invention, a middle layer of a measured object having a layer structure at least including a surface layer and the middle layer is extracted and flattened to be a same flat plane, the optical stereoscopic structure image is reconstructed with the flattened middle layer as the reference layer, the three-dimensional converted optical structure image is generated, and at least the three-dimensional converted optical structure image is imaged and displayed on the display device, whereby the structure information with the middle layer in the measured object having the layer structure as a basal plate can be visually determined.
