A seat support mechanism comprising: a lifter configured to adjust a height of a seat cushion; a link mechanism disposed between a base supporting a cushion frame of the seat cushion and the cushion frame and configured to be displaced when the height is adjusted, wherein the lifter includes: a clutch mechanism configured to provide a rotational force; a rotational force transmission mechanism including a rotor (323; 327) that rotates by a rotational force transmitted from the clutch mechanism; and a torsion bar (330, 340) that has one end connected to a rotation center of the rotor (323; 327) of the rotational force transmission mechanism of the lifter and the other end connected to the link mechanism and extends in a width direction of the cushion frame, and the torsion bar (330, 340) has both a function of, when the lifter adjusts the height, adjusting a height of the cushion frame by elasticity thereof using the other end connected to the link mechanism as a fixed end and a function of, when external vibration is inputted, absorbing the vibration by elasticity thereof using the one end connected to the rotor (323, 327) of the rotational force transmission mechanism as a fixed end on the basis of movement of the link mechanism based on displacement of the cushion frame relative to the base characterized in that the link mechanism includes: a pair of front link mechanisms located on a front portion of the cushion frame and disposed so as to be spaced from each other in the width direction; and a pair of rear link mechanisms located on a rear portion of the cushion frame and disposed so as to be spaced from each other in the width direction, the torsion bar includes: a front torsion bar corresponding to the front link mechanisms; and a rear torsion bar corresponding to the rear link mechanisms, the front torsion bar has one end connected to the rotor (323, 327) of the rotational force transmission mechanism and the other end connected to front movable links (413, 414) of the front link mechanisms, and the rear torsion bar has one end connected to the rotor (323, 327) of the rotational force transmission mechanism and the other end connected to rear movable links of the rear link mechanisms. a lifter configured to adjust a height of a seat cushion; a link mechanism disposed between a base supporting a cushion frame of the seat cushion and the cushion frame and configured to be displaced when the height is adjusted, wherein the lifter includes: a clutch mechanism configured to provide a rotational force; a rotational force transmission mechanism including a rotor (323; 327) that rotates by a rotational force transmitted from the clutch mechanism; and a torsion bar (330, 340) that has one end connected to a rotation center of the rotor (323; 327) of the rotational force transmission mechanism of the lifter and the other end connected to the link mechanism and extends in a width direction of the cushion frame, and a clutch mechanism configured to provide a rotational force; a rotational force transmission mechanism including a rotor (323; 327) that rotates by a rotational force transmitted from the clutch mechanism; and a torsion bar (330, 340) that has one end connected to a rotation center of the rotor (323; 327) of the rotational force transmission mechanism of the lifter and the other end connected to the link mechanism and extends in a width direction of the cushion frame, and the torsion bar (330, 340) has both a function of, when the lifter adjusts the height, adjusting a height of the cushion frame by elasticity thereof using the other end connected to the link mechanism as a fixed end and a function of, when external vibration is inputted, absorbing the vibration by elasticity thereof using the one end connected to the rotor (323, 327) of the rotational force transmission mechanism as a fixed end on the basis of movement of the link mechanism based on displacement of the cushion frame relative to the base characterized in that the link mechanism includes: a pair of front link mechanisms located on a front portion of the cushion frame and disposed so as to be spaced from each other in the width direction; and a pair of rear link mechanisms located on a rear portion of the cushion frame and disposed so as to be spaced from each other in the width direction, a pair of front link mechanisms located on a front portion of the cushion frame and disposed so as to be spaced from each other in the width direction; and a pair of rear link mechanisms located on a rear portion of the cushion frame and disposed so as to be spaced from each other in the width direction, the torsion bar includes: a front torsion bar corresponding to the front link mechanisms; and a rear torsion bar corresponding to the rear link mechanisms, a front torsion bar corresponding to the front link mechanisms; and a rear torsion bar corresponding to the rear link mechanisms, the front torsion bar has one end connected to the rotor (323, 327) of the rotational force transmission mechanism and the other end connected to front movable links (413, 414) of the front link mechanisms, and the rear torsion bar has one end connected to the rotor (323, 327) of the rotational force transmission mechanism and the other end connected to rear movable links of the rear link mechanisms.