A boot includes a major-diameter fastener, a first bellows, a second bellows, a minor-diameter-side bellows, and a minor-diameter fastener. The major-diameter fastener is to be fastened to a mating major-diameter member. The first bellows is disposed continuously from the major-diameter fastener. The second bellows is disposed continuously from the first bellows. The minor-diameter-side bellows is disposed continuously from the second bellows. The minor-diameter fastener is disposed continuously from the minor-diameter-side bellows, and is to be fastened to a mating minor-diameter member. The first bellows exhibits an averaged first axial rigidity. The second bellows exhibits an averaged second axial rigidity. The minor-diameter-side bellows exhibits an averaged third axial rigidity. The averaged first axial rigidity and the averaged third axial rigidity are lower than the averaged second axial rigidity.