A biological constituent concentration measuring device that can measure a biological constituent concentration highly accurately using a radiation that has come from an eardrum is provided.A measuring device for measuring concentration of a biological constituent includes: an image capturing section for capturing an image of an eardrum; a processing section for generating tilt information concerning tilt of the eardrum based on a first image capturing information obtained by capturing an image of a first area of the eardrum and a second image capturing information obtained by capturing an image of a second area of the eardrum, which is different from the first area; an infrared sensor for sensing infrared radiation that has been radiated from the eardrum; and a computing section for calculating the concentration of a biological constituent based on the infrared radiation sensed and the tilt information.