The present invention provides an immunoassay analyzer capable of discriminating between normal coloring due to a specific immunoreaction and abnormal coloring due to a cause other than the specific immunoreaction in a measurement region of a sample analysis tool. An immunoassay analyzer 1 of the present invention includes an optical detection unit 4 and a determination unit 5. The optical detection unit 4 includes an optical signal measurement unit for measuring an optical signal at each of two or more different wavelengths including a main wavelength for detecting color change due to the specific immunoreaction and a sub-wavelength(s) other than the main wavelength. The determination unit 5 includes a discrimination unit for comparing the respective optical signals at the two or more different wavelengths and discriminating between the color change due to the specific immunoreaction and color change due to a cause other than the specific immunoreaction based on a comparison criterion determined previously.