The present disclosure relates to the field of idler, and in particular, to a welded idler and manufacturing method thereof. The method comprises steps of (1) separately manufacturing at least two parts; (2) friction welding, (3) spin forming, (4) turning an inner circle and an outer end surface, (5) turning another end surface, (6) surface treatment, (7) installing a bearing, (8) installing a bearing cover, (9) painting.