A laser-ablation plasma generator generates laser-ablation plasma from a target in a vacuum vessel. An ion beam extractor generates an ion beam by extracting ions included in the laser-ablation plasma from the vacuum vessel. An ion detector detects unintended ions other than intended ions, which are obtained by ionizing the elements in the target, out of ions in the vacuum vessel and outputs a detection signal representing a value which is a number of the unintended ions or a mixing ratio of the unintended ions to the intended ions as a detection result. The ion source using the laser beam makes it possible to normally monitor unintended ions other than intended ions out of ions in the vacuum vessel.
