PURPOSE: To enable fins to be integrated with a rocket structure so as to enhance strength by making a tubular preform, fins and fin supports independently and mounting them respectively.

CONSTITUTION: A tubular perform 10, fins 30 with an interior reinforced by a honeycomb structure 36 and fin supports 20 including soles 22 are made independently by fibrous cloth impregnated with polymerizable binder. The fin supports 20 are assembled with the tubular preform 10, and the assembly is polymerized. Then the fins 30 are mounted on the fin supports 20. In this way, the fins 30 are connected to the tube without the need for metal frames, therefore thickness of the tube wall is not substantially increased. Thus, the amount of fuel carried by the tube is increased. Moreover, by integrating the soles 22 of the fin supports 20 in the structure of the preform 10, the fins 30 play a role in increasing the strength of the rocket as a whole.