The objective of the present invention is to provide a headrest that can have increased comfort and safety. This headrest is provided with: an affixed-side member provided to a headrest pillar; a mobile-side member that is joined to the affixed-side member with a mobile mechanism therebetween and that can move in the front-back direction with respect to the affixed-side member; and a front-back locking mechanism that has an engaged section and a lock member that engages the engaged section, and that locks and unlocks the movement of the mobile-side member in the front-back direction. Also, the mobile-side member has a front-side cover for supporting a head. Furthermore, the engaged section is attached to the back surface of the front-side cover.