An endoscope includes: an imaging controller configured to drive in a first operation mode for operating an imager in accordance with an input first clock signal or in a second operation mode for operating the imager in accordance with an input second clock signal different from the first clock signal; a switch configured to output, to the imaging controller, a switching signal for switching the previously set second operation mode to be driven by the imaging controller to the first operation mode; and a first generator configured to generate a first enable signal causing the switch to output the switching signal based on the first clock signal when the first clock signal is input from an external processing device, and output the generated first enable signal to the switch.