A chair with an automatic seat which cyclically inclines is configured with a forward/backward cyclically inclining mechanism (8) which supports the seat (6) supplied separate from and independent of the backrest (2) so that the seat can be inclined forward and backward and driven mechanically to incline by continuously changing its inclining angle. The inclination direction of the seat can be automatically reversed within a specified angle range. In addition, the chair is equipped with a rightward/leftward cyclically inclining mechanism (13) which is rectangularly installed beneath the forward/backward cyclically mechanism (8) to support it along with seat 6 to allow and drive inclination in the rightward and leftward directions.