A chain includes a pair of rocker joint pins inserted through laterally aligned pin holes of two adjacent link plates. The pin holes have a pair of upper and lower pin-position constraining surfaces arranged to face upper and lower flat surfaces, respectively, of each rocker joint pin with a very small clearance defined therebetween so that the rocker joint pin is always kept in position against displacement in a vertical direction relative to the link plates. When the chain is urged to warp or bend into a V shape, each of the rocker joint pins is gripped by the upper pin-position constraining surface of one of the two adjacent link plates and a warp blocking surface of the other of the two adjacent link plate. Thus, such warping of the chain does not take place.