A seat frame includes: a plate member; and a bar member joined to the plate member, the bar member including a planar portion on at least part of a side surface of the bar member, wherein the plate member and the bar member are joined to each other by a welded portion including a base portion configured to: extend in a longitudinal direction of the bar member; and have a central line positioned closer to a position at which a load from a user is applied upon use of the seat frame than a central portion of the bar member, the central portion being at a center of a length of the bar member, the length being orthogonal to the longitudinal direction of the bar member, the position being in an area of contact between the plate member and the planar portion.