A dual-polarity mass spectrometer includes an ion source, a negative ion mass analyzer, and a positive ion mass analyzer to measure both the negative and positive ion spectra of a sample material simultaneously. The ion source includes a sample surface on which the sample material is positioned, the sample material providing positive ions and negative ions when excited by a laser beam or an energetic particle stream. A first extraction electrode is connected to a voltage higher than the sample surface to attract the negative ions from the sample electrode. A second extraction electrode is connected to a voltage lower than the sample surface to attract the positive ions from the sample electrode. The negative and positive ions are analyzed simultaneously by the negative ion mass analyzer and the positive ion mass analyzer, respectively.