PURPOSE: To make the pivoting of an upper backrest part interlock with the forward and backward turning movement of a lower backrest part for the prevention of troubles by dividing a backrest seat into the upper and lower backrest parts to provide a reversible toumel mechanism between the lower backrest part and a seat and the toumel mechanism with a device for finely adjusting inclination between the upper and lower backrest parts.

CONSTITUTION: A reclining mechanism A is disposed by lower reversible toumel mechanisms 19, 19 between a seat 2 and a lower backrest part 4. Upper toumel mechanisms 42, 42 are provided between the lower and upper backrest parts 4, 5. A fine adjustment device 60 is mounted on the outer end of an upper rotary shaft 49 of the upper toumel mechanism 42 to finely adjust the inclination of the upper backrest part 5 by direct turning movement with upper inner peripheral teeth 49. Also, the upper rotary shaft 49 of the upper toumel mechanism 42 is interlocked with a lower rotary shaft 26 of the lower reversible toumel mechanism 19 through a rotary transmission member 58, driven gear 57 and intermediate drive gear 34 so that the upper backrest part 5 is inclined by the forward and backward turning movement of the lower backrest part 4.