A color irregularity detecting device includes a spectrometer which includes a dispersing element which disperses light from a measurement target and a light receiving element which receives light from the dispersing element, and a color irregularity detecting section which detects color irregularity, in which the color irregularity detecting device detects color irregularity by comparing measured values (reflectance) which are results of using the spectrometer to measure three measurement wavelengths of light among light from a measurement target region in which a predetermined color is printed on a medium to reference values corresponding to the predetermined color.