The present invention relates to a medical cast having a dual structure. The present invention provides the medical cast comprising: a skin protector coming into contact with the affected area of a patient, woven by mixing and using at least two kinds of functional fibers in order to increase adhesive strength with the skin, and manufactured such that diamond-shaped mesh holes are formed in the shape of a meshed net; an inner supporting cast formed to cover the outer side of the skin protector and comprising an inside supporting cast for absorbing sweat or body waste between the casts, an inner ventilating channel for covering the outer surface of the inside supporting cast and improving air permeability, an adhesion enhancing part for increasing the elasticity of the cast, and an inner rigidity reinforcing part for providing primary rigidity for the medical cast; and an outer supporting cast formed to cover the outer side of the inner supporting cast, impregnated with a hardening solution having hydraulic properties, and comprising an outer ventilating channel (310) formed along the circumference thereof, an adhesion enhancing part connected with the outer ventilating channel (310) so as to provide predetermined elastic force, a cutter part provided on one surface of the outer side thereof for guiding the progressing direction of a cutter blade, and outer rigidity reinforcing parts formed on both sides of the cutter part so as to provide secondary rigidity for the medical cast.