An imaging device and a processing device in which a transmission method can be switched according to a connection object are provided. An endoscope 2 which is connected to an external processing device 3 and which is capable of transmitting and receiving information to and from the processing device 3 includes: an imaging element 244 to output, as image information, a photoelectrically-converted electric signal from a plurality of pixels, a P/S converter 274 to output, as an electric signal, image information output by the imaging element 244, an E/O converter 273 to output, as an optical signal, the image information output by the imaging element 244, and a selector 244k to select, based on identification information of the processing device 3, one of the P/S converter 274 and the E/O converter 273 as an output unit to output the image information.
