A double-folding-type seat with a headrest, which is adapted for use with an automobile, said double-folding-type seat with the headrest including: a seat cushion having a forward end portion adapted to be rotatably mounted on a floor of the automobile; an engagement piece provided to a rear end portion (SC-1) of the seat cushion, said engagement piece being normally disposed near to said floor of the automobile and displaceable with said seat cushion; said seat cushion is rotatable forwardly from a horizontal use position thereof toward an upright position thereof; a seat back having a lower end portion rotatably mounted on said floor of the automobile, said seat back being rotatable forwardly from an upright use position thereof toward a horizontal position thereof; and said headrest being normally mounted on a top (SB-1) of said seat back, wherein the headrest is removable from said top of said seat back, when the seat back is rotated forwardly to said horizontal position thereof; said double-folding-type seat with the headrest including: a pair of stays extending from a bottom surface of said headrest, said pair of stays being configured to be detachably mounted in said top of said seat back; and a headrest attaching portion provided to said bottom surface of said headrest, said headrest attaching portion being so configured to permit insertion therein of said engagement piece of said seat cushion; wherein the headrest is attachable on the seat cushion when said seat cushion is in said upright position thereof by inserting said engagement piece of the seat cushion in said headrest attaching portion. a seat cushion having a forward end portion adapted to be rotatably mounted on a floor of the automobile; an engagement piece provided to a rear end portion (SC-1) of the seat cushion, said engagement piece being normally disposed near to said floor of the automobile and displaceable with said seat cushion; said seat cushion is rotatable forwardly from a horizontal use position thereof toward an upright position thereof; a seat back having a lower end portion rotatably mounted on said floor of the automobile, said seat back being rotatable forwardly from an upright use position thereof toward a horizontal position thereof; and said headrest being normally mounted on a top (SB-1) of said seat back, wherein the headrest is removable from said top of said seat back, when the seat back is rotated forwardly to said horizontal position thereof; said double-folding-type seat with the headrest including: a pair of stays extending from a bottom surface of said headrest, said pair of stays being configured to be detachably mounted in said top of said seat back; and a headrest attaching portion provided to said bottom surface of said headrest, said headrest attaching portion being so configured to permit insertion therein of said engagement piece of said seat cushion; wherein the headrest is attachable on the seat cushion when said seat cushion is in said upright position thereof by inserting said engagement piece of the seat cushion in said headrest attaching portion. a pair of stays extending from a bottom surface of said headrest, said pair of stays being configured to be detachably mounted in said top of said seat back; and a headrest attaching portion provided to said bottom surface of said headrest, said headrest attaching portion being so configured to permit insertion therein of said engagement piece of said seat cushion; wherein the headrest is attachable on the seat cushion when said seat cushion is in said upright position thereof by inserting said engagement piece of the seat cushion in said headrest attaching portion.