Patent ID: 8905485

Claim:
A seat back frame comprising: a main frame that defines a frame of a seat back of a main seat, the main frame having a side frame provided on both sides of the main frame in the width direction, and an upper frame that connects upper portions of the side frames together; and an auxiliary frame that defines a frame of a seat back of an auxiliary seat adjacent to the main seat in a width direction, and that is integrally connected with the main frame, wherein at least a portion of the main frame includes a first tube-shaped member, the first tube-shaped member having a first open portion that opens toward a side with the auxiliary seat in the width direction, at least a portion of the auxiliary frame includes a second tube-shaped member, and an end portion of the second tube-shaped member is a fitting structure that fits within the first open portion of the first tube-shaped member, and a portion of the fitting structure is welded such that the main frame and the auxiliary frame are integrally connected along the upper frame of the main frame.