The purpose of this invention is to obtain a compact particle beam irradiation apparatus by mounting on a rotary gantry an accelerator, which has a reduced weight by using a superconducting hollow core coil.The particle beam irradiation apparatus (59) includes a particle beam circular accelerator (51), a beam transport system (54), and an irradiation field forming apparatus (56) supported by the rotary gantry (60). The particle beam circular accelerator (51) includes a pair of superconducting coils (3a,3b) arranged symmetrically with respect to an acceleration orbit plane (12), and a pair of pole chip (7a,7b) arranged symmetrically with respect to the acceleration orbit plane (12) at an inner side of the superconducting coils (3a, 3b), for forming a magnetic field distribution from a magnetic field generated by the superconducting coils (3a, 3b) to make a charged particle beam (16) circle in an acceleration cavity (11). The pole chip (7a,7b) has a thin portion (26) having a thinnest wall thickness which is the thickness between an inward surface (18) and an outward surface (22), the thin portion (26) being disposed such that more than half of the thin portion (26) exists in an outer peripheral side of an intermediate line (29) between a coil axis (17) and an outer peripheral end of the pole chip (7a,7b), an inward side and an outward side of the thin portion (26) being flat, and the wall thickness of a center portion including the coil axis (17) being the thickest.本發明的目的在於將藉由採用超導空蕊線圈從而輕量化的加速器搭載在旋轉機架,來獲得小型的粒子線照射裝置。本發明的粒子線照射裝置(59)係具備有:被旋轉機架(60)所支持的粒子線圓形加速器(51)、射束傳輸系統(54)、及照射野形成裝置(56),而該粒子線圓形加速器(51)係具備有:一對超導線圈(3a,3b),係以相對於加速軌道面(12)呈對稱之方式配置;以及一對磁極翼(7a,7b),係配置於超導線圈(3a,3b)之內側,且以相對於加速軌道面(12)呈對稱之方式配置,並且從藉由超導線圈(3a,3b)所產生的磁場來形成使帶電粒子射束(16)在加速空腔(11)環繞的磁場分佈。磁極翼(7a,7b)係組構成:具有使屬於內向面(18)和外向面(22)間之厚度的壁厚為最薄的薄壁部(26),且以一半以上存在於較線圈軸(17)和磁極翼(7a,7b)之外周端部的中間的中間線(29)還靠外周側之方式配置薄壁部(26),並且薄壁部(26)的內向面側及外向面側為平坦者;內含線圈軸(17)的中央部之前述壁厚為最厚者。1‧‧‧低溫恆溫器2‧‧‧固定構造體3a、3b‧‧‧超導線圈4a、4b‧‧‧主動屏蔽線圈5a、5b、6a、6b‧‧‧傳熱板7
