ION GUIDE AND MASS SPECTROMETER

An ion guide (222) is for use in transport of an ion incident from an upstream side toward a downstream side. The ion guide includes 2n rod electrodes (n is an integral number greater than or equal to 2) equally spaced and surrounding an ion optical axis (C) that is a central axis of a flight path of the ion, a voltage applying unit (30) that applies a radio-frequency voltage to the 2n rod electrodes, and a controller (43) that controls the voltage applying unit (30). The controller (43) prompts the voltage applying unit (30) to apply a radio-frequency voltage that generates, in a space surrounded by the 2n rod electrodes, an electric field which is a 2n-multipole electric field superimposed by a higher-order electric field component than the 2n-multipole electric field.