The invention relates to a double-end input or output resonator for a vacuum electronic device, belonging to the technical field of vacuum electronics, and relates to vacuum electronic devices such astraveling wave tubes, backward wave tubes, klystrons, free electron lasers, oro tubes and the like. The resonator comprises N resonant cavities arranged in parallel, N is a positive integer, one endof each resonant cavity is connected with the same waveguide through a respective coupling hole, and the other end of each resonant cavity is connected with another waveguide through a respective coupling hole. When the two-terminal input/output structure is used as the input element, the electromagnetic wave is input at both ends in phase, and when the two-terminal input/output structure is usedas the output element, the electromagnetic wave excited in the resonant cavity is output from both ends in phase through the coupling hole. Whether as an input structure or an output structure, the two-terminal structure modulates both ends of the band electron beam simultaneously, which makes the electron beam speed increase or decrease uniformly, and improves the efficiency of the input/output structure.