PURPOSE: To obtain an easy to handle microwave tube device by arranging a high power traveling-wave tube or klystron so that the lower end face of an electron gun can become higher than that of an electron beam focussing field device and a guide rail or moving wheel on the lower end face of the electron beam focussing field device.

CONSTITUTION: A high power microwave tube 1 is installed on a permanent magnet assembly 2 and mounted on a bench 3. A non-magnetic spacer is arranged between the permanent magnet assembly 2 and bench 3. Since this non- magnetic spacer 6 is fixed in the permanent magnet assembly 2, it can be moved simultaneously when the permanent magnet assembly is moved. Since an electron gun 4 is placed in the combined body of the permanent magnet assembly and non- magnetic spacer by the arrangement of this non-magnetic spacer 6, it will not collide with the bench when it is moved. As a result, since the microwave tube need not be removed from the permanent magnet or lifted up, it can be handled easily. The microwave tube can be handled more easily by fitting a moving wheel in this permanent magnet assembly.