The invention provides a chain (100) comprises guide rows (101) and non-guide rows (102) and connecting pins 103 connecting the guide and non-guide rows in a chain longitudinal direction, and travels in slidable contact with a chain guide (3). First and second link plate composing the guide and non-guide rows are slidable-contact link plates 150 each having a convex back surface that slidably contacts a traveling surface of the chain guide. Cross-sections of a curved portion 154a of the back surface 154 in the chain longitudinal and chain widthwise directions are both substantially arc-like longitudinal curve Ce and widthwise curve Ct. A radius of curvature Rt of the widthwise curve Ct is not smaller than a radius of curvature Re of the longitudinal curve Ce. This improves chain durability reducing friction loss of the chain.