PROBLEM TO BE SOLVED: To provide a balloon having excellent flexibility and capable of suppressing axial elongation of the balloon, and a manufacturing method thereof.SOLUTION: A balloon 30 to be disposed on a medical catheter includes a freely expandable cylindrical part 42 composed of a birefringent high polymer material. The ratio of the number of orientation distributions calculated by dividing the number of orientation distributions in a circumferential direction of the cylindrical part 42 by the number of orientation distributions in an axial direction of the cylindrical part 42 is adjusted to be less than 1.5 so that axial elongation percentage of the cylindrical part 42 is 6% or less under a condition of pressurization of 1-13 atm.SELECTED DRAWING: Figure 1【課題】良好な柔軟性を有しかつバルーンの軸方向伸びを抑制し得るバルーンおよびその製造方法を提供する。【解決手段】医療用カテーテルに配置されるバルーン３０であって、複屈折性の高分子材料から構成される拡張自在の筒状部４２を有する。筒状部４２の周方向配向分配数を筒状部４２の軸方向配向分配数によって除して算出される配向分配数の比率は、１～１３ａｔｍの加圧条件下における筒状部４２の軸方向伸び率が６％以下になるよう、１．５未満に調整されている。【選択図】図１
