A site position can be detected using transmitted light or reflected light which does not include an excitation wavelength according to a configuration of a biochip 60. When reflected light is used, a light source 21 is actuated. Light from the light source 21 passes through a barrier filter 22 and is bent by a dichroic mirror 23 and passes through a dichroic mirror 3 and illuminates the biochip 60. The reflected light in the biochip 60 enters a CCD camera 13. An output signal of the CCD camera 13 is sent to a computation part 51 and a position of a site on the biochip 60 is detected in the computation part 51.