An image scanning apparatus has an organic CMOS image sensor mounted in a base, and a photoreceptive surface of the image sensor is exposed on a top side of the base. A subject is placed directly on the photoreceptive surface, and the subject and the photoreceptive surface are covered up with a cover light-tightly. Thus the image sensor detects only chemiluminescent light from the subject. As for a fluorochrome-labeled subject, the subject placed directly on the photoreceptive surface is irradiated with excitation light from a light source mounted in the cover. The image sensor is provided with a filter for blocking the excitation light from its photoelectric conversion layers, so the image sensor detects only fluorescent rays generated from the excited fluorochrome-labeled subject. The image scanning apparatus needs no redundant space in perpendicular direction to the photoreceptive surface.