INDICATOR

An indicator (31) is to be attached to a target object that is the target of determination of a degradation state, the indicator having color components to be extracted by a degradation state determination apparatus that includes a degradation state model and a color change database for determining the degradation state of the target object. The indicator includes a medium layer having printed thereon an identifier (32) and a color pattern (33) having a plurality of colors applied to different positions, the plurality of colors having different sensitivities to a degradation factor.