A tilting fitting device enables a chair seat to be tiltable forwards and backwards against spring force of tilt-resisting springs, the tilting fitting having an upper part that is fastenable to the chair seat and a lower part that is fastenable to a chair base and tiltably connected to the upper part, wherein the tilting resistance is adjustable by adjusting spacing between the tilt-resisting springs and distance of each spring from a respective side of a tilting axis for the upper part. An actuating element is arranged for simultaneous engagement with two support members, an actuating element, along a part of each of its two sides in the element's direction of motion. On movement of the actuating element in the longitudinal direction of the tilting axis, it is adapted to cause rotation of the support members and springs mounted thereon, thereby changing the spacing of the springs.