PURPOSE: To plan to make the size compact and to improve the load stability by a method wherein, in connection with imprivements in the construction of the anode, panes are so fixed that they are placed at a preset angle to an axis of an anode cylinder.

CONSTITUTION: A plurality of panes 6 are fixed radially to the inside wall of an anode cylinder 5 and each of every two panes 6 is linked together with two kinds of large and small strap rings 7, 8. Each pane 6 of a magnetron is fixed to the inside wall of the anode cylinder 5 in such a manner that it is placed at a preset angle θ to an axis B. Consequently, even if the height H of the pane 6 is assumed, for instance, 10x, its hight H in the axial direction can be 8x, so that the configuration of a magnetic circuit may be made compact. In addition, because an electronic spoke is formed so that it tilts at an angle of θ, the length of the anode becomes h and as a result the load stability becomes equivalent to what has had the pane with the conventional height h.