A radiation measuring system includes a whole-body counter having upper and lower radiation detectors that are located in front of a measurement space, which has an inlet passage and is located in a housing, and that detects respective internal radiations of a measurement target and first and second internal radiations of a body region corresponding to one of a thyroid gland, a lung, a whole body, or a hypogastrium, and a processor controlling determination of an internal radioactive contamination location of the measurement target, based on a ratio of the first and second internal radiations, applying the optimal measurement geometry corresponding to the ratio of the first and second internal radiations, and detecting the first and second internal radiations of a body region corresponding to the internal radioactive contamination location.
