A rewriteable card of the invention is composed of a thermally reversible thermosensitive recording material which changes reversibly between a slightly opaque state and a transparent state depending on a given heating condition wherein the rewriteable card includes a reference slightly opaque portion at the part thereof having the reflectance equivalent to a slight opacity state of the thermally reversible thermosensitive recording material in an early stage or a last stage of use of the rewriteable card. A method of judging the life of the rewriteable card is based on the result of detection of the reflectance on a printing slightly opaque portion and that on the reference slightly opaque portion, and a printing apparatus is provided with a card life judging device employing the judging method.