An object of the present invention is to provide a BNCT treatment apparatus and a BNCT treatment method capable of further reducing radiation damage to normal cells when irradiating a neutron beam to an affected part of a patient. A BNCT treatment apparatus includes an accelerator neutron source and a moderator for decelerating neutrons generated by the accelerator neutron source. A boron drug is administered to a patient, and the neutrons decelerated by the moderator are applied to the affected area of the patient. The drug treatment effect ratio (CBE) becomes 4 or more depending on the absorbed dose of the affected part of the patient due to irradiation of the drug. [Selection diagram] Fig. 1【課題】患者の患部に中性子線を照射する場合に、正常細胞への放射線ダメージをより低減できるＢＮＣＴ治療装置、およびＢＮＣＴ治療方法を提供する。【解決手段】ＢＮＣＴ治療装置は、加速器中性子源と、加速器中性子源が発生する中性子を減速させる減速体とを備え、患者にはホウ素薬剤が投与され、減速体が減速させた中性子が患者の患部へ照射されることによる患者の患部の吸収線量によって、薬剤治療効果比（ＣＢＥ）が４以上となる。【選択図】図１
