A processing device includes a signal processing unit configured to: input first and second pixel signals from an image sensor having pixels for receiving light from a subject illuminated with pulsed light and generating a pixel signal, the first pixel signal being a one-frame signal read at read timing at least a part of which is included in an illumination period of the pulsed light, the second pixel signal being a one-frame signal read after the one frame of the first pixel signal; and generate a one-frame third pixel signal by synthesizing first and second overlap pixel signals, the first overlap pixel signal being defined as the first pixel signal corresponding to an overlap line of the pixels in which the illumination period of the pulsed light is overlapped with the read timing, the second overlap pixel signal being defined as the second pixel signal corresponding to the overlap line.