An ion source, a first control electrode for controlling an ion beam emitted by the ion source, a detector for detecting scattered particles, and a second control electrode for controlling the ion beam, which is directed from the ion source toward a sample, as well as the scattered particles, are arranged on the same axis along with the sample. The ion beam directed from the ion source toward the sample, and the scattered particles, which are scattered from the sample and are directed toward the detector, are caused to converge. By using an Einzel-type lens as the second control electrode, charged particles and neutral particles constituting the scattered particles are provided with a difference in speed. The detector possesses an anode plate which is divided into the form of concentric, circular plates or concentric arc-shaped plates, and each divided anode plate provides a detection output which contains information relating to a distribution of the scattering angles of the scattered ions.