The purpose of the present invention is to irradiate an irradiation target with a small beam size, even for low-energy charged particle beams. This particle beam irradiation device (58) is provided with a vacuum duct (6, 7) which forms a vacuum region for transmitting the charged particle beam (1), a vacuum window (8) from which the charged particle beam (1) is emitted from the vacuum region, scanning electromagnets (2, 3) which scan the charged particle beam (1) in a direction orthogonal to the beam axis, a monitor device (67) which has a position monitor (5) which detects the transmission position and the beam size of the charged particle beam (1), a low-scattering gas filling chamber (39) which covers the vacuum window (8) and in which the monitor device (67) is arranged on the downstream side, and an irradiation management device (20) which controls irradiation of the charged particle beam (1), and is characterized in that the low-scattering gas filling chamber (39) is arranged such that the relative positions of the monitor device (67) and the vacuum window (8) in the beam axis direction can be changed to a desired position, and, when the charged particle beam (1) is irradiated, the low-scattering gas filling chamber (39) is filled with a low-scattering gas having lower scattering than air.La présente invention a pour but d'irradier une cible de rayonnement par un faisceau de petite dimension, même pour des faisceaux de particules chargés à basse énergie. Ce dispositif de rayonnement par émission de faisceau de particules (58) comporte un conduit sous vide (6, 7) qui forme une région de vide pour transmettre le faisceau de particules chargées (1), une fenêtre de vide (8) à partir de laquelle le faisceau de particules chargées (1) est émis à partir de la région de vide, des électroaimants de balayage (2, 3) qui balayent le faisceau de particules chargées (1) dans une direction orthogonale à l'axe du faisceau, un dispositif de surveillance (67) qui a un dispositi
