An endoscopic system comprises an endoscope system, an endoscopic position detecting apparatus, and an image processing apparatus. The endoscope system enables endoscopic examinations. The endoscopic position detecting apparatus detects the three-dimensional positions of the distal part of the endoscope in a body cavity. The image processing apparatus estimates the shape of an object entity visualized by the endoscope. The image processing apparatus is used as a means for grasping the shape of an object entity in a body cavity. For this purpose, the insertion unit of an electronic endoscope is inserted into the body cavity of a patient lying down on a patient couch. Specifically, a main unit of the image processing apparatus is connected to a video processor over a cable, and receives an image signal (R, G, and B signals and a sync signal) sent from the video processor. The main unit of the image processing apparatus estimates relative shapes according to successive image signals representing the object entity and being sent from the video processor. The main unit of the image processing apparatus then calculates the absolute shape of the object entity according to the position data of the distal part of the electronic endoscope sent from a main unit of the endoscopic position detecting apparatus.