A method of producing a long roll retardation film comprising the sequential steps of: (a) casting a film forming material on an endless support to form a long roll film; (b) stretching the long roll film in a lateral direction of the long roll film while both edges of the long roll film are held employing a plurality of clips for each of the edges in a tenter (First Process); (c) reducing distances in the lateral direction between the clips holding the both edges of the long roll film while the edges of the long roll film are held continuously from First Process with the clips (Second Process); (d) enlarging the distances in the lateral direction between the clips holding the both edges of the long roll film while the edges of the long roll film are held continuously from Second Process with the clips (Third Process).