A method for manufacturing a connecting member configured to contribute to the connection between a center wing box of an aircraft and a wing of the aircraft, the method comprising the set of the following steps: - a step of manufacturing preforms (4a, 4b, 4c, 4d, 4e) made of composite material forming the connecting member; - a step of assembling the preforms (4a, 4b, 4c, 4d, 4e) by heat treatment in order to form the connecting member, characterized in that the step of manufacturing preforms (4a, 4b, 4c, 4d, 4e) corresponds to a step of manufacturing five preforms (4a, 4b, 4c, 4d, 4e), and in that the manufacturing step comprises: - a first manufacturing substep (E1a) consisting in manufacturing a main preform in the form of a strip having a first longitudinal axis and having a first surface opposite to a second surface, and - four second manufacturing substeps (E1b) consisting in manufacturing one first L-shaped preform, one second L-shaped preform, one third L-shaped preform and one fourth L-shaped preform, each L-shaped preform corresponding to a profile section having a second longitudinal axis the transverse cross section of which is L-shaped comprising a first web (7a, 8a, 9a, 10a) perpendicular to a second web (7b, 8b, 9b, 10b), and in that the assembly step comprises: - a preforms-assembly substep consisting in assembling the preforms (4a, 4b, 4c, 4d, 4e) manufactured in the first manufacturing substep (E1a) and the second manufacturing substeps (E1b), the preforms (4a, 4b, 4c, 4d, 4e) being assembled so that the connecting member formed by the preforms (4a, 4b, 4c, 4d, 4e) has a cruciform transverse cross section by ensuring that: • the first web of the first L-shaped preform is butted against the first web of the second L-shaped preform, • the second web of the first L-shaped preform and the second web of the second L-shaped preform are butted against the first surface of the main preform, • the first web of the third L-shaped preform is butted against the first web of the fourth L-shaped preform, • the second web of the third L-shaped preform and the second web of the fourth L-shaped preform are butted against the second surface of the main preform, • the first longitudinal axis of the main preform is parallel to the second longitudinal axes of the L-shaped preforms (4a, 4b, 4c, 4d), - a heat treatment substep consisting in heat treating the preforms (4a, 4b, 4c, 4d, 4e) assembled in the assembly substep. - a step of manufacturing preforms (4a, 4b, 4c, 4d, 4e) made of composite material forming the connecting member; - a step of assembling the preforms (4a, 4b, 4c, 4d, 4e) by heat treatment in order to form the connecting member, - a first manufacturing substep (E1a) consisting in manufacturing a main preform in the form of a strip having a first longitudinal axis and having a first surface opposite to a second surface, and - four second manufacturing substeps (E1b) consisting in manufacturing one first L-shaped preform, one second L-shaped preform, one third L-shaped preform and one fourth L-shaped preform, each L-shaped preform corresponding to a profile section having a second longitudinal axis the transverse cross section of which is L-shaped comprising a first web (7a, 8a, 9a, 10a) perpendicular to a second web (7b, 8b, 9b, 10b), and in that the assembly step comprises: - a preforms-assembly substep consisting in assembling the preforms (4a, 4b, 4c, 4d, 4e) manufactured in the first manufacturing substep (E1a) and the second manufacturing substeps (E1b), the preforms (4a, 4b, 4c, 4d, 4e) being assembled so that the connecting member formed by the preforms (4a, 4b, 4c, 4d, 4e) has a cruciform transverse cross section by ensuring that: • the first web of the first L-shaped preform is butted against the first web of the second L-shaped preform, • the second web of the first L-shaped preform and the second web of the second L-shaped preform are butted against the first surface of the main preform, • the first web of the third L-shaped preform is butted against the first web of the fourth L-shaped preform, • the second web of the third L-shaped preform and the second web of the fourth L-shaped preform are butted against the second surface of the main preform, • the first longitudinal axis of the main preform is parallel to the second longitudinal axes of the L-shaped preforms (4a, 4b, 4c, 4d), • the first web of the first L-shaped preform is butted against the first web of the second L-shaped preform, • the second web of the first L-shaped preform and the second web of the second L-shaped preform are butted against the first surface of the main preform, • the first web of the third L-shaped preform is butted against the first web of the fourth L-shaped preform, • the second web of the third L-shaped preform and the second web of the fourth L-shaped preform are butted against the second surface of the main preform, • the first longitudinal axis of the main preform is parallel to the second longitudinal axes of the L-shaped preforms (4a, 4b, 4c, 4d), - a heat treatment substep consisting in heat treating the preforms (4a, 4b, 4c, 4d, 4e) assembled in the assembly substep.