To provide an image reader, for a fluorescence detecting system, by which an image can be read out with good accuracy irrespective of an image carrier.

Laser-exciting light-source means 1, 2, 3 which emit beams of laser light are provided. An image-carrier mounting base 13 which is formed of a transparent material and on which an image carrier carrying a fluorescent image formed by a fluorescent substance excited by the beams of laser light so as to emit fluorescence is mounted is provided. A laser-light scanning means 9 by which the image carrier mounted on the image-carrier mounting base 13 is scanned via the image-carrier mounting base 13 from the lower part of the image-carrier mounting base 13 by the beams of laser light emitted from the laser-exciting light-source means 1, 2, 3 is provided. In addition, a light detecting means 20 by which fluorescence emitted from the image carrier installed at the lower part of the image-carrier mounting base 13 is detected photoelectrically is provided. The image-carrier mounting base 13 is provided with an image-carrier housing part 13a which houses the image carrier. Then, a substance W whose refractive index is higher than that of air and whose refractive index is closer to that of the image carrier is housed at the inside of the image-carrier housing part 13a.