A method of manufacturing T-shaped stringers made of composite material, including a second shaping step for shaping laminates into L-shaped preforms, which includes providing a set of tools formed by a fixed tool comprising a lower portion and an upper portion, and a moveable tool comprising a lower element and an upper element. It also includes the segment of the laminate intended for the foot of the preform being located between the lower portion and the upper portion of the fixed tool, and the segment of the laminate intended for the web of the preform being located between the lower element and the upper element of the moveable tool. It further includes vertically moving the moveable tool to progressively bend the web of the preform supporting it on a vertical wall of the fixed tool. The end of its web adopts a rounded shape.