To provide a method of manufacturing a circular boom antenna such that when an antenna element is fixed to a boom, the antenna element can be fixed to the boom while making the sectional shape of the boom circular only by inserting the antenna element into tube wall holes of the boom and pressing the boom in upward and downward directions.

The hollow antenna element is made to penetrate a pair of tube wall holes of the boom, and a wall member of a first quadrant and a wall member of a second quadrant are deformed toward a reception part by applying force from an outer peripheral direction. The deformation causes a press streaks to move toward the reception part to be pressed against a peripheral wall of the antenna element and to dig into a peripheral wall of the antenna element. The wall member of the first quadrant and the wall member of the second quadrant are bent respectively to shorten the gap between upper end edges of the both, and the upper end edges of the wall member of the first quadrant and the wall member of the second quadrant are joined together to make the sectional shape of the boom circular.