To accurately accommodate a screw head into a threaded screw hole.

In a frame 29 of a high-frequency circuit unit, a mounting hole 30 with a diameter which is slightly larger than the largest of the shell of a coaxial connector is formed, and a screw hole 32 is formed at a position that is close to the mounting hole 30, and at the same time is connected to the mounting hole 30, and corresponds to a set of diagonal screw holes of a flange. The threaded screw hole 32 of the frame 29 can surround the screw neck of a countersunk head screw 11 by 270 degrees, larger than by 180 degrees in its circumferential part, and at the same time the minimum width for connection is set smaller than the diameter of the screw neck.