PURPOSE: To fix a tubular body quickly and surely by simple process by inserting a tubular body into inserting holes pierced in facing walls of a cylindrical body and expanding the tubular body by compressing it from both ends to the center.

CONSTITUTION: For instance, an antenna element is fixed to an arm in the following way. An antenna element 3 is inserted into inserting holes 32, 32 pierced in facing walls of an arm made of plastics. The arm 30 is then placed on receptacles 26, 26 and the element 31 is positioned between open holding pieces 8a, 11a and 8b, 11b. Hydraulic cylinders 14a, 14b are driven, and the part of the element 31 exposed to outside of the arm is held by pieces 8a, 11a and 8b, 11b. A hydraulic cylinder 23 is driven and a holding device 3A is moved in the direction to approach to a holding device 3B, and the element 31 is compressed in axial direction. The part of the element 31 which is not held between pieces 8a, 11a and 8b, 11b is expanded by this compressing operation, and the element 31 is fixed to the arm 30.