To provide an armrest having a detent mechanism and freely setting a turning range of an armrest pad without making the detent mechanism restrict the turning angle of the armrest pad relative to an elbow support.

This armrest is provided with the armrest pad 1 for resting the elbow of a seating person, the elbow support 2 horizontally turnably supporting the armrest pad 1, and the detent mechanism formed between the armrest pad 1 and the elbow support 2 and restrictingly stopping the armrest pad 1 at a predetermined angle. The detent mechanism is provided with a stationary member 3 having a plurality of detent engagement recesses 31k around its outer circumferential face 31b and a movable member 4 turnably operated with the armrest pad 1 and having an engagement element 41k sequentially and elastically engaged with the plurality of detent engagement recesses 31k. The stationary member 3 is attached to the side of the elbow support 2 and the movable member 4 is attached to the side of the armrest pad 1.