In order to improve seating comfort and vibration absorbency, a structure including a first torsion bar unit 70 disposed in the rear of a seat cushion, and a second torsion bar unit 80 disposed in the front of the seat cushion, and a base net 60 stretched between a rear supporting frame 74 of the first torsion bar unit 70 and a front supporting frame 84 of the second torsion bar unit 80, is provided. Owing to the elastic force of a front torsion bar 81 of the second torsion bar unit 80 positioned in the front of the seat, a sense of stroke at the time of seating is enhanced. Owing to the elastic force of a rear torsion bar 71 of the first torsion bar unit 70 positioned in the rear of the seat, similarly to the conventional structure, a load of a seated person can be sufficiently received and a stable seating comfort can be obtained. Since both the first torsion bar unit 70 and the second torsion bar unit 80 work together to dampen vibration inputted during driving, vibration absorbency is more enhanced than ever.