This research was made to suggest a functional and fitted prototype of swallow-tailed coat for sports dance. We established the basic posture of standard dance from literature investigations, and grasped the changes of the body side-surface by motions through the gypsum-experiments with a man in twenty. The unfolded gypsum shells were overlapped on the basic swallow-tailed coats pattern drafted by their size of experimenter. From our results through analysis, our pattern of the swallow-tailed coats for sports dance was designed considering their functional and structural character. In case of upper body with the greatly increased shoulder width of garment and with the decreased front. When moving, owing to the rising of the armpit point, the side-line becomes longer with the shoulder length decreased greatly. In case of sleeves, the length of sleeves back increased greatly by the arm-bending motions while sleeve height becomes lowered.