A rare case of left atrial myxoma associated with ruptured chordae tendineae is presented. The patient was 70-year-old woman, and was diagnosed to have a left atrial myxoma. The myxoma was extirpated together with the atrial septum from which tumor developed. After removal of the myxoma, a ruptured strut chordae tendineae of anterior leaflet was also detected and resutured to the original papillary muscle. The cause of the torn chordae is presumed to be so-called "wrecking ball effect", and to be myxomatous degeneration of the valve.