Abstract: Provided is a method of producing recycled reinforcing fibers capable of efficiently recovering reinforcing fibers, even with a solvent method, from a fiber-reinforced resin material comprising a resin component having a chemical structure with basic properties. A method of producing recycled reinforcing fibers, the method including: a step of treating a fiber-reinforced resin material comprising a resin and reinforcing fibers with an acidic solution comprising an acid; and a step of treating the fiber-reinforced resin material with a treatment solution comprising an oxidizing agent to dissolve at least part of the resin of the fiber-reinforced resin material in the treatment solution, wherein the resin comprises a resin component having a chemical structure with basic properties.

Abstract: Provided are a reinforcing-fiber recovery reactor and a method of producing recycled reinforcing fibers capable of maintaining the shape and orientation of reinforcing fiber bundles when the reinforcing fibers are separated from a fiber-reinforced resin material by a solvent method. Provided is a reinforcing-fiber recovery reactor used for recovering reinforcing fibers from a fiber-reinforced resin material by a solvent method, the reactor comprising: a reaction vessel that can accommodate the fiber-reinforced resin material and a solvent; and a fixing mechanism comprising a pressing member capable of pressing the fiber-reinforced resin material, the fixing mechanism being capable of fixing the accommodated fiber-reinforced resin material by pressing the fiber-reinforced resin material with the pressing member.