A method of manufacturing a reinforcement layer comprises a preparatory step of preparing to-be-wound fiber, and a formation step of forming an uncured sheet layer including multiple layers of the to-be-wound fiber stacked on an outer circumferential surface. In the formation step, the to-be-wound fiber is wound on the outer circumferential surface in such a manner that, regarding an outer layer of the uncured sheet layer and an inner layer of the uncured sheet layer closer to the outer circumferential surface than the outer layer and adjacent to the outer layer in a stacking direction of the to-be-wound fiber, two end portions of the outer layer are located between two end portions of the inner layer in an axis direction extending along a center axis of a winding target member.