PURPOSE: To provide the chair for rotating in the forward and backward directions, while oscillating in the left and the right directions.

CONSTITUTION: A main column 6 protrudes the tip part from a bearing 10 provided in a housing 5, and also, is provided so as to be oscillatable centering around the bearing 10, and in a base end part of the main column 6, a first connecting rod 11 for executing a reciprocating motion is provided, and in the main column 6 in an adjacent part of the bearing 10, a second connecting rod 21 for executing a reciprocating motion to a lever 20 fixed integrally with the main column is provided, and to the tip part of the main column 6, a seat part of the chair is connected, and the chair oscillates in the left and the right directions by an oscillating motion of the main column 6 and rotates in the forward and backward directions by a forward/backward rotational motion of the main column.