An endoscope adapter including a light emitting diode includes: a detachable portion to be attached to an adapter attaching portion provided on a distal end portion of an insertion portion, the insertion portion including inside thereof at least one image-forming optical system an adapter main body including an adapter side observation optical system whose optical axis is coincident with an optical axis of the image-forming optical system a contact pin which enables power supply to the light emitting diode to be turned on when the detachable portion is attached to the adapter attaching portion and a resistor arranged in a space formed in the endoscope adapter to determine a type of the endoscope adapter.
