A seat frame for a folding chair includes a U-shaped front frame, a linear rear frame and a seat cushion. The front frame has a first support surface between an upper surface and a lower surface of the front frame, the first support surface having a contour the same as that of the front frame. The rear frame has a second support surface between an upper surface and a lower surface of the rear frame, the second support surface having a contour the same as that of the rear frame. The seat cushion is clamped between the first and second support surfaces in a horizontal position. The peripheral edges of the seat cushion are thereby in tight contact with the first and second support surfaces. Brackets are then used to connect the front frame and the rear frame that surround the seat cushion therein.