To provide a ball joint capable of restraining the abrasion of a resin sheet over a long period because lubricant shortage hardly occurs.

The resin sheet 17 is intervened between a housing 16 and a spherical head 23 of the ball joint 12. The resin sheet 17 includes a tubular part 21 surrounding the spherical head 23 and a bottom part 22 which plugs one end of the tubular part 21 and is opposed to the bottom of a storage chamber 19 and is integrally formed with the other end of the tubular part 21 configured as an opening 50 in cup-shaped manner and is provided with a plurality of concave grooves 52 reaching from the bottom part 22 side to the opening 50 on the inside surface. Each of the concave grooves 52 is configured so that its depth in the opening 50 side is deeper than that in the bottom part 22 side.

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