A link mechanism for a link device in a stretching machine configured to stretch a film, the link mechanism comprising: a pair of rail holders (24a, 24b); a base member bridging the pair of rail holders (24a, 24b); a link plate (22, 23) having one end rotatably coupled to one of the pair of rail holders (24a, 24b) and the other end rotatably coupled to another link mechanism; and a clip provided at one end of the base member and configured to grip the film, wherein each of the rail holders (24a, 24b) includes: a guide roller (51a, 51b, 52a, 52b) whose both ends in an axial direction are open and which moves along a rail (13, 14) while rotating; a shaft (54, 55) penetrating the guide roller (51a, 51b, 52a, 52b); and a bearing (56a, 57a, 56b, 57b) interposed between the guide roller (51a, 51b, 52a, 52b) and the shaft (54, 55) and rotatably supporting the guide roller (51a, 51b, 52a, 52b), wherein a cover member (71, 72) that covers the bearing (56a, 57a, 56b, 57b) is provided on at least one of one end side of the guide roller (51a, 51b, 52a, 52b) in the axial direction and the other end side of the guide roller (51a, 51b, 52a, 52b) in the axial direction and wherein the bearing (56a, 57a, 56b, 57b) includes an inner ring, an outer ring, a rolling element, arranged between the inner ring and the outer ring, a seal configured to cover a gap between the inner ring and the outer ring, a lubricant being filled in the gap, wherein the cover member (71, 72) is arranged outside the seal so as to overlap the seal, and the gap of the bearing (56a, 57a, 56b, 57b) is doubly covered by the seal and the cover member (71, 72). a pair of rail holders (24a, 24b); a base member bridging the pair of rail holders (24a, 24b); a link plate (22, 23) having one end rotatably coupled to one of the pair of rail holders (24a, 24b) and the other end rotatably coupled to another link mechanism; and a clip provided at one end of the base member and configured to grip the film, wherein each of the rail holders (24a, 24b) includes: a guide roller (51a, 51b, 52a, 52b) whose both ends in an axial direction are open and which moves along a rail (13, 14) while rotating; a shaft (54, 55) penetrating the guide roller (51a, 51b, 52a, 52b); and a bearing (56a, 57a, 56b, 57b) interposed between the guide roller (51a, 51b, 52a, 52b) and the shaft (54, 55) and rotatably supporting the guide roller (51a, 51b, 52a, 52b), a guide roller (51a, 51b, 52a, 52b) whose both ends in an axial direction are open and which moves along a rail (13, 14) while rotating; a shaft (54, 55) penetrating the guide roller (51a, 51b, 52a, 52b); and a bearing (56a, 57a, 56b, 57b) interposed between the guide roller (51a, 51b, 52a, 52b) and the shaft (54, 55) and rotatably supporting the guide roller (51a, 51b, 52a, 52b), wherein a cover member (71, 72) that covers the bearing (56a, 57a, 56b, 57b) is provided on at least one of one end side of the guide roller (51a, 51b, 52a, 52b) in the axial direction and the other end side of the guide roller (51a, 51b, 52a, 52b) in the axial direction and wherein the bearing (56a, 57a, 56b, 57b) includes an inner ring, an outer ring, a rolling element, arranged between the inner ring and the outer ring, a seal configured to cover a gap between the inner ring and the outer ring, a lubricant being filled in the gap, wherein the cover member (71, 72) is arranged outside the seal so as to overlap the seal, and the gap of the bearing (56a, 57a, 56b, 57b) is doubly covered by the seal and the cover member (71, 72).