A large electron tube includes: a tubular collector; and a magnetic body disposed outside the collector and having no axial symmetry with respect to a center axis of the collector. This makes it possible to inhibit parasitic oscillation that occurs inside the collector.

A large electron tube includes: a tubular collector; and a magnetic body disposed outside the collector and having no axial symmetry with respect to a center axis of the collector. This makes it possible to inhibit parasitic oscillation that occurs inside the collector.