PURPOSE: To make it possible to measure heavy and light specimen forming atoms with one apparatus at the same time by projecting a primary ion beams on the surface of a specimen, and detecting the backward scattering component of the primary ions from the surface of the specimen and recoiled radiation particles.

CONSTITUTION: A primary ion beams is modulated in a pulse state with a chopper 5 and inputted into a specimen 2. When the beam hits specimen forming atoms heavier than the primary ions, the backward scattering ions and the neutralized particles of the ions are recoiled in the direction forming a small angle θ and detected with a microchannel plate 3. The signal is displayed on a CRT 9 as the relation between the time and the intensity of the detected particle signal. Then, a counting device 6 starts counting at the fall-down of pulses applied in the chopper 5. Therefore, the speed distribution of the scattering particles is drawn. The specimen constituting elements can be determined and the quantities are determined based on the distribution. When the beam hits the light specimen forming atoms, the recoiled particles from the specimen surface are recoiled in the direction forming a large angle with the primary ion beams. The particles are detected with a microchannel plate 4, and the speed distribution is drawn on the a CRT 9. Thus the spectrums of the recoiled specimen atoms can be distinguished.