An image pickup apparatus has an image sensor recording image information; a dustproof glass for keeping hermeticity of the periphery of the image sensor, placed in front of the image sensor; an optical filter removably placed in front of the dustproof glass; and a camera mount placed in front of the optical filter. The image pickup apparatus further has a parfocal adjusting device in which a focal position where the optical filter is demounted can be adjusted so as to be nearly equal to the focal position where the optical filter is mounted.