Provided is an analysis device in which light from a sample (7) fixed into a test piece (1) is acquired by an image sensor (5) via an optical system formed by a lens (3) and a diaphragm (4) so as to obtain concentration information. By using a wide-range light source (12) for illuminating the test piece (1) in combination with an optical filter (13) for arbitrarily selecting a wavelength of lightacquired by the image sensor (5), it is possible to reduce the measurement fluctuation caused by a change of light amount distribution of the light source (12).