To provide an electron beam irradiation apparatus controlling condensation of steam accompanying air blow onto a window foil from a nozzle unit and further controlling corrosion or the like of the window foil due to a deposition of condensate.

The nozzle unit 12 for blowing cooling air against the window foil in an electron beam irradiation window section of an electron beam irradiation apparatus main body is connected in communication with a cooling air supply unit 4, and the unit 4 includes a cooling air blower 41, and a dehumidifier 43. The blower 41 supplies air supplied from the dehumidifier 43 to the nozzle unit 12, and the dehumidifier 43 comprises a refrigerant circuit for compressing a refrigerant by a compressor, condensing it by a condenser and guiding it to an evaporator via an expansion system and a dehumidifier blower for sucking air from outside, making the air pass through to bring it into contact with the evaporator and discharging it from a dehumidifier discharge opening 43b.