To provide a manufacturing method of a circular boom antenna in which an antenna element can be fixed to a boom by only having the antenna element penetrated through a pipe wall hole of the boom and vertically applying pressure on the boom when fixing the antenna element to the boom.

A boom is compressed in a vertical direction to bring an upper arcuate-wall element and a lower arcuate wall element closer each other, to curve right and left evaginated-wall elements so as to evaginate in a direction where a distance between them increases so that a cross-sectional shape of the boom becomes an approximately perfect circle and to reduce respective gaps between free edges of right and left ribs which face each other. Concave pressing regions disposed on each free edge of four ribs in the upper side and the lower side are brought closer to the opposing rib, the ribs respectively bite into the peripheral wall of correspondent antenna element arranged between the ribs, and an inner periphery hole edge of a pipe wall hole is pressure-weld with the antenna element by decreasing the vertical direction distance so that rotation of the antenna element and its movement in the axial direction are prevented.