Isotope identification imaging of nuclear fuel material or explosives concealed in a drum or container in which nuclear reactor fuel or radioactive waste are sealed is realized while ensuring high precision, high reliability, and safety. A sample 31 is irradiated with laser Compton photon beams 21 and 22 generated by a collision between an electron beam 12 and polarized laser light 16 and 20. An isotope in the sample is identified using nuclear resonance fluorescence, and the spatial distribution thereof is imaged. In so doing, a nuclear level of an isotope whose emission direction of nuclear resonance fluorescence is dependent on the planes of polarization of the incident LCS photon beams is used.