Abstract: A sealed neutron tube is provided, in which an insulating structure is designed to be solid to enhance the shock-proof performance thereof, an ion beam drawn out from an ion source is pulsated more rapidly, and the lifetime of a target is increased without substantially increasing the filling amount of the Tritium. The sealed neutron tube (1) includes a metal housing (20), an ion source (5) disposed and sealed within the metal housing for ionizing a Deuterium gas, an accelerating electrode (4) charged with a high voltage, disposed and sealed within the metal housing and facing the ion source, and a target (3) disposed within the accelerating electrode and absorbing Tritium and the like therein. An outer wall (20) is constructed by a metal housing, and a ceramic insulating member (11) is disposed within the metal housing. Since the accelerating electrode is held by this insulating member, the outer wall of the sealed neutron tube has enhanced shock-proof performance.