To provide a locking mechanism for inclining a backrest of a reclining chair or the like at an appropriate angle and retaining/locking the attitude of the backrest, especially having a simple mechanism, and capable of minutely selecting and setting the angle, and changing the angle very easily.

The locking adjusting mechanism 4 includes an inner-toothed or outer-toothed fixed gear 20 and a plurality of displacement gears 30 to be engaged with the fixed gear. The respective displacement gears 30 are formed to be operated at a time in the engaging direction by a cam 40. In a normal state, the displacement gears 30 are engaged with the fixed gear 20 by the cam 40, and the attitude of a movable frame 2 relative to a fixed frame is retained/locked. When the movable frame 2 is appropriately tilted, the displacement gears 30 can be separated from the fixed gear 20 by the operation of the cam 40, and the movable frame 2 is tilted while the engaged state of the gear members is temporarily released.