To obtain a video signal level required for positioning of an image even in an image pickup state at a low illuminance in an image pickup device having an A/D converter for analog/digital-converting output signals of an image pickup element.

The image pickup device has the image pickup element to receive an image pickup light from an object to be photographed and to output as analog video signals by executing photoelectric conversion corresponding to the received light and the A/D converter for analog/digital-converting the analog video signals. The magnification to amplify digital video signals to be outputted from the A/D converter is varied corresponding to levels of the digital video signals. When the video level required for the positioning of the image pickup device for the fundus oculi examination or the like, for example, is 512 gradations or more of the half of 1,023 gradations, the positioning can be executed even at a low illuminance by adjusting a bit-shift amount of a video level amplification circuit 6.