A virtual field of view of a virtual endoscope, which is positioned at a position corresponding to a detected position of an endoscope in a 3D medical image, is determined based on a position of a structure of interest, the corresponding position and a posture of the endoscope, and an angle of view of the endoscope, such that the position of the structure of interest is contained within the virtual field of view and the virtual field of view has continuity with the field of view of the endoscope. From the 3D medical image inputted, a virtual endoscopic image having the determined virtual field of view with the view point thereof being the corresponding position of the endoscope is generated. The generated virtual endoscopic image is displayed on a WS display.
