Process for manufacturing a structural component (1, 1', 1", 1''', 1"" ) made of composite material comprising a skin (2) and at least one stiffening stringer (3, 3', 3", 3"', 3"") applied rigidly and integrally to one face (2a) of the skin (2); the process comprises the following steps: a) arranging on a tool (12, 12', 12", 12''', 12"") a plurality of first layers (4; 4a', 4b'; 4"; 4'"'; 4a"", 4b"", 4c"") of uncured or p re-cured composite material forming the stringer (3, 3', 3", 3'", 3"") presenting a longitudinal axis (A) and having a raised portion (7, 7', 7", 7''', 7"" ) protruding from at least one flange (8) extending parallel to the longitudinal axis (A) and along a lying surface that is flat or is a surface of revolution (S);) b) arranging on said tool (12, 12', 12", 12''', 12"") a plurality of second layers of uncured or p re-cured composite material forming said skin (2); c) making a face (2a) of said skin (2), parallel to said lying surface (S), and said flange (8) of said stringer (3, 3', 3", 3'", 3"") adhere to each other; d) applying predetermined temperature and pressure on the assembly thus formed so as to compact said layers together, possibly curing the uncured material and rigidly joining said skin (2) to said stringer (3, 3', 3", 3'", 3"" ); and e) performing a cutting operation on the free end side edge/s (13) of said flange (8) in a transversal direction with respect to said lying surface (S); and f) cover said end side edge/s (13) of the end of said flange (8) with a coating of composite material so as to seal outwards the layers (4; 4a', 4b'; 4 "; 4'"; 4a"", 4b"") forming said flange (8).