Abstract: The klystron of the invention comprises cavities 5 with face walls 7 and drift tubes 8. There are annular slots 9in the face walls 7 and drift tubes 8, said annular slots 9 accommodating plates 10 rigidly attached thereto, said plates 10 being made of a nonmagnetic material. The height of the plates 10 is less than half the height of the body 6 of the cavity 5. The length of the plates 10 is equal to the half-difference between the inner diameter of the body 6 and the inner diameter of the drift tube 8. The length of the inner circumference of the body 6 is more than ten times the total thickness of the plates 10.The klystron of the invention can be used in radioelectronic units to provide for higher stability of their output characteristics.