To provide a configuration solving such a problem that it is difficult to impart the lubricity on a surface of a bearing, in a joint where reciprocating motion can be converted to rotary motion through a crankshaft and a connecting rod.

A rocking joint 30 is disclosed where bearing surfaces rock with respect to each other with no sliding between the surfaces. Pull rods 31 couples from a left cylinder via a bridge 42. The pull rods 31 include: a pull rod body 32, a center element 34, a bearing element 36, and an end cap 38, all held together via bolts 40. The bridge 42 includes cross-pin extensions 44 extending outwardly toward the pull rods. In the bearing element 36, a back side of the bearing element 36 that sits against a surface of an opening 46 includes a convexly curved surface.