To provide an electron beam irradiation window capable of preventing failure of window foil especially fatigue failure without thickening the window foil.

For a device removing sulfuroxide and/or nitrogenoxide in exhaust gas by scanning and irradiating electron beam to the exhaust gas, one each crosspiece 3 and 4 is provided to an electron beam source side window irradiating electron beam α to a reaction chamber R as a processed gas chamber and to the middle of width direction of the reaction chamber side window. The electron beam source side window foil 1 and reaction chamber side window foil 2 are supported by the crosspieces 3 and 4, the middle of both window foils 1 and 2 is made a cooling gas chamber C, the cooling gas is supplied from the width direction outer edge of the electron beam side window and the cooling gas is exhausted from the width direction outer edge of the reaction chamber side window so that the cooling gas flow 5 reverses in the middle of width direction of the window foils 1 and 2.