Provided is an accelerator provided with a rotating condenser capable of performing frequency modulation of a high-frequency electric field in correspondence with emission energy that differs for each rotation direction. The accelerator includes an accelerating electrode (4) for accelerating charged particles, an accelerating cavity (5) for supplying power to the accelerating electrode (4) to generate a high-frequency electric field, and a rotation for modulating a resonance frequency of the accelerating cavity (5). A condenser (10). The rotating condenser (10) rotates in both the forward and reverse directions, and takes a time change of capacitance different for each rotation direction. Frequency modulation is performed in such a manner that a time change of the capacitance different for each rotation direction is made to correspond to a different emission energy.回転方向ごとに異なる出射エネルギーに対応させて高周波電場の周波数変調を行うことが可能な回転コンデンサー備えた加速器を提供する。加速器は、荷電粒子を加速させる加速電極（４）と、加速電極（４）に電力を供給し、高周波電場を発生させる加速空洞（５）と、加速空洞（５）の共振周波数を変調させる回転コンデンサー（１０）とを備える。回転コンデンサー（１０）は、順方向及び逆方向の双方に回転し、回転方向ごとに異なる静電容量の時間変化をとる。回転方向ごとに異なる静電容量の時間変化をそれぞれ異なる出射エネルギーに対応させて周波数変調を行う。
