There are provided a retardation film, a manufacturing method thereof, and a liquid crystal display device including the same. The retardation film includes 1) an acrylic film, 2) a coating layer of a negative C-type material, and 3) a primer layer including a copolymer containing an aromatic vinyl-based unit and a maleic acid-based unit, provided between the acrylic film and the coating layer of the negative C-type material. The retardation film may be used in an in-plane switching mode liquid crystal display device.