A headrest to be mounted to a top of a seat back with a headrest pillar and a plurality of headrest guides that each has a head, the headrest guides configured to height-adjustably support the headrest pillar and being attached to the seat back such that the heads of the headrest guides are exposed from the top of the seat back, the headrest comprising: a plurality of recesses on a bottom of the headrest, the recesses facing the head of the headrest guide, wherein a surface of each of the recesses is set to be separate from the heads of the headrest guide; a headrest body comprising a shifting mechanism for moving the headrest in the front-rear direction relative to the headrest pillar; and a bottom cover disposed on the bottom of the headrest body, the bottom cover including the plurality of recesses, wherein the headrest pillar comprises a plurality of support posts, a plurality of first openings are provided in the bottom of the headrest body, the first openings being aligned with the respective support posts to introduce the headrest pillar into the headrest body, a plurality of second openings are provided in the bottom cover, the second openings being aligned with the respective support posts and with the plurality of first openings such that the respective support posts extend through the plurality of second openings, a plurality of tubular plugs are provided in the bottom cover, the plugs standing upwards from respective peripheral edges of the plurality of second openings and aligned with the respective support posts. the plugs being inserted into the headrest body through the plurality of first openings, the plurality of recesses provided below the plugs, and the bottom cover has a middle portion between one recess below one plug of the plurality of plugs and another recess below another plug of the plurality of plugs, the middle portion protruding from the bottom surfaces of the recesses of the bottom cover. a plurality of recesses on a bottom of the headrest, the recesses facing the head of the headrest guide, wherein a surface of each of the recesses is set to be separate from the heads of the headrest guide; a headrest body comprising a shifting mechanism for moving the headrest in the front-rear direction relative to the headrest pillar; and a bottom cover disposed on the bottom of the headrest body, the bottom cover including the plurality of recesses, wherein the headrest pillar comprises a plurality of support posts, a plurality of first openings are provided in the bottom of the headrest body, the first openings being aligned with the respective support posts to introduce the headrest pillar into the headrest body, a plurality of second openings are provided in the bottom cover, the second openings being aligned with the respective support posts and with the plurality of first openings such that the respective support posts extend through the plurality of second openings, a plurality of tubular plugs are provided in the bottom cover, the plugs standing upwards from respective peripheral edges of the plurality of second openings and aligned with the respective support posts. the plugs being inserted into the headrest body through the plurality of first openings, the plurality of recesses provided below the plugs, and the bottom cover has a middle portion between one recess below one plug of the plurality of plugs and another recess below another plug of the plurality of plugs, the middle portion protruding from the bottom surfaces of the recesses of the bottom cover.