The present invention is to present a measuring device which can conduct stable extraction and measurement of interstitial fluid. The measuring device comprises: a device body which comprises an extraction part for extracting body fluid from a living body and a measuring part for measuring a biological component contained in the extracted body fluid; a holding member which holds the device body and has an opening part for defining a measurement area on the living body; and a mounting member for mounting the holding member on the living body; wherein the measurement area on the living body is defined by the opening part when the holding member is mounted on the living body by the mounting member.