A height-adjustable pillow comprising: a lower member; an upper member disposed on the lower member, the upper member being displaceable up and down with respect to the lower member; and a lifting unit adjusting a height of the upper member by displacing the upper member, wherein the lifting unit comprises: a rotary member provided on a surface of one of the lower member and the upper member that faces the other of the lower member and the upper member such that the rotary member is rotatable about a vertical axis, the rotary member comprising a slope upwardly inclined in one direction along a circumference thereof about the axis and a plurality of holding step portions formed on the slope to continuously extend along a length of the slope such that the plurality of holding step portions are positioned at different heights; and a contact member provided on the other one of the lower member and the upper member such that the contact member is able to come into contact with one of the plurality of holding step portions depending on an angle of rotation of the rotary member, wherein each of the plurality of holding step portions comprises a stepped surface and a connecting surface, the stepped surfaces of the plurality of holding step portions are arranged at predetermined distances in the length of the slope such that the stepped surfaces are spaced apart and positioned at different heights from each other, and the connecting surfaces of the plurality of holding step portions comprise inclined surfaces connecting the stepped surfaces having different heights, respectively, such that the contact member is displaced up and down along one of the connecting surfaces to move to an adjacent one of the stepped surfaces when the rotary member is rotated. a lower member; an upper member disposed on the lower member, the upper member being displaceable up and down with respect to the lower member; and a lifting unit adjusting a height of the upper member by displacing the upper member, wherein the lifting unit comprises: a rotary member provided on a surface of one of the lower member and the upper member that faces the other of the lower member and the upper member such that the rotary member is rotatable about a vertical axis, the rotary member comprising a slope upwardly inclined in one direction along a circumference thereof about the axis and a plurality of holding step portions formed on the slope to continuously extend along a length of the slope such that the plurality of holding step portions are positioned at different heights; and a contact member provided on the other one of the lower member and the upper member such that the contact member is able to come into contact with one of the plurality of holding step portions depending on an angle of rotation of the rotary member, a rotary member provided on a surface of one of the lower member and the upper member that faces the other of the lower member and the upper member such that the rotary member is rotatable about a vertical axis, the rotary member comprising a slope upwardly inclined in one direction along a circumference thereof about the axis and a plurality of holding step portions formed on the slope to continuously extend along a length of the slope such that the plurality of holding step portions are positioned at different heights; and a contact member provided on the other one of the lower member and the upper member such that the contact member is able to come into contact with one of the plurality of holding step portions depending on an angle of rotation of the rotary member, wherein each of the plurality of holding step portions comprises a stepped surface and a connecting surface, the stepped surfaces of the plurality of holding step portions are arranged at predetermined distances in the length of the slope such that the stepped surfaces are spaced apart and positioned at different heights from each other, and the connecting surfaces of the plurality of holding step portions comprise inclined surfaces connecting the stepped surfaces having different heights, respectively, such that the contact member is displaced up and down along one of the connecting surfaces to move to an adjacent one of the stepped surfaces when the rotary member is rotated.