An apparatus for measuring and fixing the three-dimensional location of medical instrument that can be easily placed at a desired location by a user. In addition, a medical apparatus for measuring the three-dimensional locations of an apparatus fixed at an end portion of a cancer and an external apparatus and fixing the apparatus at an end portion of the cancer, which can be easily placed at a desired location by a user and carries out the location-fixing and measuring at the same time. The apparatus is applicable for various medical fields such as the measurement of the location and orientation of an external apparatus, the measurement of relative locations of a medical instrument contacted to an end-portion of a cancer and the object body, and the fixation of the instrument at a desired location.