wherein the metallic unpainted injection molding is molded by injecting a metallic resin into a molding part inside an injection mold through a plurality of gates to be molded, wherein at least a groove line is molded in a boundary section where metallic resins meet each other in the molding part,

wherein the metallic unpainted injection molding includes a penetration hole of a shape which is formed to extend along a vehicle width direction in a center portion thereof, and includes a skid plate which is formed with the at least a groove line including a corresponding groove in a predetermined section starting from opposite corners of the penetration hole, respectively,

wherein the at least a groove line is respectively formed at opposite sides of the skid plate based on the vehicle width direction,

wherein the at least a groove line includes a first groove line and a second groove line,

wherein the first groove line is connected to a first lower side corner of the penetration hole based on a vehicle height direction, and is disposed to be inclined along an external surface of the skid plate corresponding to a first side corner of the penetration hole, and

wherein the second groove line is connected to a second lower side corner of the penetration hole based on the vehicle height direction, and is disposed to be inclined along the external surface of the skid plate corresponding to a second side corner of the penetration hole,

wherein at least a flake line occur in a boundary section where metallic resins from different gates among the plurality of gates meet each other in the molding part, and

wherein at least a groove line is molded in the boundary section to prevent the at least a flake line being exposed to an outside.