An endoscope includes a lens unit, a diaphragm for brightness adjustment, a diaphragm for type determination and an image pickup device. The diaphragm for type determination has an image formation portion an image of which is formed in a light receiving section, a position and a number of the image formation portion provided for the diaphragm for type determination differing according to a plurality of adapters. The endoscope further includes a CPU that determines a type of an adapter by determining a position and a number of the image formation portion an image of which is formed in the light receiving section.
