MASS SPECTROSCOPE

PROBLEM TO BE SOLVED: To prevent introduction efficiency of ions from decreasing and to save the trouble for cleaning operation.SOLUTION: There is provided a mass spectroscope such that an ion introduction hole of an electrode is divided into a first region, a second region, and a third region, the first region and/or third region has a center axis direction of an ion introduction hole different from a flow direction of ions in an ion introduction hole of the second region, and axes of the ion introduction holes of the first region and third region have eccentric position relationship.