To provide an electron-beam tube capable of uniformly irradiating an electron beam on an irradiation object matter by avoiding fluctuation of an electron-beam output.

The electron-beam tube comprises a vacuum vessel comprising a tubular member, an anode covering a front side opening of the tubular member and having an opening part permitting the electron beam to pass through and an emission section sealing the opening part and having a window permitting the electron beam to pass through, an electron beam generator disposed in the vacuum vessel and a cylinder member connected to the anode in the vacuum vessel and having an electric potential equivalent to that of the anode. The cylinder member is disposed so that the opening periphery of the tubular member is positioned frontward of a virtual line passing the end part of the window and the rear-side end of the opening in the anode.