A measuring image acquisition means 2 acquires a 3-D measuring image in which a phantom filled with the radioactive material into a necessary part is measured with a SPECT system. A measuring image Fourier transform means 4 operates the 3-D measuring image with the 3-D Fourier transform. An actual image acquisition means 6 acquires a 3-D actual image of the part of the phantom which is filled with the radioactive material. An actual image Fourier transform means 8 operates a 3-D actual image with the 3-D Fourier transform. An error image calculation means 10 divides each Fourier transform value of the 3-D Fourier transform measuring image by each Fourier transform value of the corresponding 3-D Fourier transform actual image and acquires a 3-D Fourier transform error image. A point spread function calculation means 12 operates the 3-D Fourier transform error image with the inverse Fourier transform and determines the point spread function image by calculation. A measurement accuracy processing means 14 calculates the measurement accuracy of the measuring apparatus based on the point spread function image.