The invention provides a carrier device for a thermal transfer medium comprising a spool for winding and supporting a thermal transfer sheet or a thermal transfer receiving sheet, wherein a mark containing a coloring material which absorbs an electromagnetic wave of a predetermined wavelength null1 and emitting an electromagnetic wave of a wavelength null2 different from the wavelength null1 is provided on a region in a surface of the carrier device capable of being irradiated with an electromagnetic wave. The invention provides a discrimination method and a printer each of which utilizes such a carrier device capable of executing at least one process among the kind identification, the fake goods determination and the use amount calculation for the thermal transfer sheet or the thermal transfer receiving sheet based on a detection of the mark.