Chair and seat support mechanism

A seat support mechanism, wherein the seat support mechanism is configured to move supporting locations to a seat to the front, rear, right, and left by combining:

• a front support structure and a rear support structure configured to directly or indirectly support a bottom surface of the seat at least at two locations in a front-rear direction;
• and a left support structure and a right support structure configured to directly or indirectly support the bottom surface of the seat at two locations in a left-right direction, the supporting locations being configured to draw a trajectory along which a tip side in a movement direction of the seat is downwardly inclined in accordance with the movement regardless of whether the seat moves in the front, rear, left, or right direction, and the seat support mechanism further comprises:
• a return-force generation mechanism configured to generate a return force, in accordance with an amount of the movement from the reference position by raising the center of gravity of the seat regardless of whether the seat moves in the front, rear, left or right direction.