An imaging device captures an object. The imaging device includes: an imaging unit that captures the object and outputs video data; a memory unit that stores therein the video data from the imaging unit; a video signal processing unit that reads the video data from the memory unit at a frame rate lower than a frame rate at which the video data are written into the memory unit and performs signal processing on the video data; an output interface unit that outputs to an external device the video data; and a control unit that outputs to the imaging unit an instruction to capture the specific number of frames and to write video data into the memory unit as an exposure period signal, instructs the video signal processing unit to output the video data from the memory unit, and outputs to the external device an imaging period signal.