Quadrupole accelerator and method for manufacturing quadrupole accelerator

The invention relates to a quadrupole accelerator and a manufacturing method of the quadrupole accelerator. Provided are: a quadrupole accelerator capable of adjusting the resonant frequency in a high-frequency accelerator to a desired frequency without using a tuner; and a technique relating to the quadrupole accelerator. A quadrupole accelerator is provided with a center member (11), a first side member (12), and a second side member (13). A cut surface (CS1) is provided on the inner surface of a portion of the first wall section (12b) that forms the first hollow cylinder (HC1). A cut surface (CS2) is provided on the inner surface of a portion of the first wall section (12b) that forms the second hollow cylinder (HC2). A cut surface (CS3) is provided on the inner surface of a portion of the second wall section (13b) that forms the third hollow cylinder (HC3). A cut surface (CS4) is provided on the inner surface of a portion of the second wall section (13b) that forms the fourth hollow cylinder (HC4). Each c