Four rod electrodes (50a to 50d) for separating ions according to a mass-to-charge ratio are held by two rod holders (51). The rod holders (51) are attached to metal holder sustaining stands (52) provided on a bottom surface of a vacuum housing (1). A coating film layer (10) is formed by a black nickel plating process on parts of wall surfaces in the vacuum housing (1), an inlet lens (4), and an outlet lens (6), the parts facing a quadrupole mass filter unit (5). The emissivity of the coating film layer (10) is higher than that of Al or the like, and thus radiant heat from the quadrupole mass filter unit (5) is efficiently absorbed by the coating film layer (10). Therefore, heat generated in the rod holders (51) due to dielectric loss is efficiently dissipated, and deformation of the rod holders can be reduced.