Four rod electrodes (50a to 50d) for separating ions according to a mass-to-charge ratio are held by a rod holder (51). The rod holder (51) is placed on a metal holder sustaining stand (52) provided on a bottom surface of a vacuum housing (1), and is fixed while being pressed by a fixation band (53) fixed to the holder sustaining stand (52) with screws (56). The fixation band (53) has a coating film layer (532) formed by a black nickel plating process on the entire surface of a main member (531) made from phosphor bronze. The coating film layer (532) has high emissivity, and thus heat transferred from the rod holder (51) to the fixation band (53) is efficiently radiated into the vacuum housing (1). Therefore, heat generated in the rod holder (51) due to dielectric loss is efficiently dissipated, and deformation of the rod holder can be reduced.