PROBLEM TO BE SOLVED: To provide a seat frame using the hemming technique. SOLUTION: An inner frame 211 and an outer frame 212 having flanges 211a and 212a respectively along the rims are disposed to face each other across a gap at least in a part in each side frame 21 of the cushion frame 20, and the flanges 211a and 212a are fixed to each other along the whole peripheral edge by the hemming processing. As the whole rim is hemmed, the inner frame 211 and the outer frame 212 are securely fixed to each other. Furthermore, as thin sheet-like inner frame 211 and outer frame 212 are used, the weight of the side frame can be reduced. As the inner frame 211 and the outer frame 212 face each other across a gap at least in a part, the strength necessary against the compression/tension is secured for the side frame by inserting a bead foam body into the gap. COPYRIGHT: (C)2010,JPO&INPIT