An object of the present invention is to prevent lowering of introduction efficiency of ions and to reduce labor for a cleaning operation. In order to solve the above problems, the present invention provides a mass spectrometer where ion introduction hole of an electrode is divided into a first region, a second region, and a third region, a central axis direction of the ion introduction hole in both or either one of the first region and the third region is different from a flow direction axis of the ion inside the ion introduction hole in the second region, and axes of the ion introduction hole in the first region and the third region are in an eccentric position relationship.