An endoscope system includes, in order to automatically detect a type of optical adapter and to generate to display an excellent image according to an intended purpose by performing an image signal processing control corresponding to the type of the optical adapter, a signal processing circuit for performing various image signal processings on an image signal from an image-pickup element, a plurality of optical adapters each including an image-formation optical system, adapter discriminating section, and LED, the optical adapters being detachably and selectively provided to the distal end of the endoscope section, and an apparatus main body including an image processing section for performing predetermined signal processing on the image signal from the signal processing circuit, an adapter detection section for detecting the adapter discrimination section, and a controller for controlling the whole endoscope system. At least driving control of the LED and various signal processing controls on the image signal obtained by the image-pickup element are performed based on the detection result of the adapter discrimination section by the adapter detection section.