To provide an electron beam irradiator capable of decreasing non- irradiation fields which are positioned on both edges of an agitation vessel in the crosswise direction, even though width of the agitation vessel is not decreased.
This electron beam irradiator is equipped with the tray-like agitation vessel 10, an electron beam accelerator 2, and a drive mechanism 14a, wherein the agitation vessel 10 receives granules of a material to be irradiated 12, the electron beam accelerator 2 irradiates the material 12 in the agitation vessel 10 with electron beams 6, and the drive mechanism 14a swings the agitation vessel 10 in the direction as shown by an arrow D so as to make the vessel draw an circular arc around a point 34 which is positioned outside and below the agitation vessel.