To provide an accelerator which is small-sized and capable of extracting a beam of variable energy, and a particle beam therapy system with the same.SOLUTION: An accelerator comprises: an acceleration high frequency application device which is capable of performing frequency modulation and applies an acceleration high frequency for accelerating a beam； a high frequency kicker 70 which applies an extraction high frequency of which the frequency is different from the acceleration high frequency, for extracting the beam； a peeler magnetic field region 44 and a regenerator magnetic field region 45 each including a magnetic field component of two or more poles and forming a disturbance magnetic field region consisting of a high-order magnetic field including a magnetic field component of at least four poles； a shim of a magnetic body； and a septum electromagnet 43 including an inner periphery side septum coil conductor, an outer periphery side septum coil conductor, a coil conductor connection part and a lead-out part of a coil.SELECTED DRAWING: Figure 2【課題】小型で、かつ可変エネルギーのビームの取出しが可能な加速器とそれを備えた粒子線治療システムを提供する。【解決手段】周波数変調が可能であり、ビームを加速する加速高周波を印加する加速高周波印加装置と、加速高周波とは周波数が異なり、ビームを取出すための取出し高周波を印加する高周波キッカ７０と、２極以上の極数の磁場成分を含み、少なくとも４極磁場成分を含む高次磁場よりなる擾乱磁場領域を形成するピーラ磁場領域４４、リジェネレータ磁場領域４５と、磁性体のシム、および内周側セプタムコイル導体、外周側セプタムコイル導体、コイル導体接続部、コイル口出し部を有するセプタム電磁石４３と、を備えている。【選択図】図２
