Radiation measurement device and method

In the present invention, a total dose is calculated on the basis of the γ-ray spectrum. A direct ray dose is calculated on the basis of a peak portion, in the spectrum, which includes the total energy peak. The direct rays are considered to be γ-rays that have directly reached a radiation detector from a γ-ray source. By subtracting the direct ray dose from the total dose, a scattered ray dose is calculated. The scattered rays are considered to be γ-rays that have reached the radiation detector after a scattering stage. In the case of using a gamma camera provided with a radiation detector comprising a plurality of detector elements, a spectrum is calculated by each of the detector elements, and a direct ray dose and a scattered ray dose are calculated.