An inner diameter measuring device (100) for measuring the inner diameter of a conduit is provided with: a first channel member (120) and a second channel member (140) which individually communicate with a balloon member (110) a fluid pouring mechanism (130) an outward flow closing mechanism (150) and a volume measuring means (160). The fluid pouring mechanism (130) pours a non-compressive fluid into the balloon member (110) either through the first channel member (120) or through the second channel member (140). The outward flow closing mechanism (150) closes either the first channel member (120) or the second channel member (140). The volume measuring means (160) measures the volume of the non-compressive fluid to be measured which is additionally filled into the balloon member through the other of the first and second channel members by means of the fluid pouring mechanism (130), the additional filling being that which is performed with the balloon member (110), the first channel member (120), and the second channel member (140) filled with the fluid and with either the first channel member (120) or the second channel member (140) closed by the outward flow closing mechanism (150).La présente invention concerne un dispositif de mesure dun diamètre interne (100) destiné à mesurer le diamètre interne dun conduit, qui est doté de : un premier élément de canal (120) et un second élément de canal (140) qui communiquent individuellement avec un élément de ballonnet (110) un mécanisme de versement de fluide (130) un mécanisme de fermeture du flux sortant (150) et un moyen de mesure du volume (160). Le mécanisme de versement de fluide (130) verse un fluide non compressif dans lélément de ballonnet (110) soit par le premier élément de canal (120) soit par le second élément de canal (140). Le mécanisme de fermeture du fluide sortant (150) ferme soit le premier élément de canal (120) soit le second élément de canal (140). Le moyen de mesure du volume (160) mesure le volu
