A chair includes a support mechanism 2 interposed between a leg 1 and a seat 3, wherein the support mechanism 2 is arranged below the seat 3, is configured to each individually and movably support the seat 3, at least at two locations in a front-rear direction and two locations in a left-right direction, along a predetermined trajectory, and the support mechanism 2 includes: a seat inclining mechanism Q or a seat inclining function configured to downwardly incline a tip side in a movement direction of the seat 3 in accordance with movement of the seat 3, and further includes: a center-of-gravity movement mechanism P or a return-force generation mechanism configured to generate a return force in a direction of returning the seat 3 having moved from a reference position (S) in a front-rear or left-right direction, to the reference position (S) by using a center-of-gravity movement.