T-.MeV gamma-ray imaging has become an indispensable technology in many fields, especially medical science. A full ray-tracing of MeV gamma-rays, however, has not been realized because of its intrinsic difficulty. Collimation is one of the conventional quasi-imaging methods and is used in SPECT, although the quality of the image is not satisfying. The Compton method, which provides one of the two directions required for the ray-tracing, is still under development. The only method to detect the direction of a gamma-ray pair is PET, the use of which is restricted because of its high cost and limited isotopes. A full ray-tracing gamma-ray camera for single photons would give us great advances in nuclear medicine.Here we report on the new method and instrument, which has not only realized a complete reconstruction of the Compton process but also provided a strong background-rejection with the novel micro-tracking device.