A device for adjusting a position of a headrest for a vehicle includes: a stay mounted on a seatback frame; a main frame including a rotation guide hole, inserted into and mounted on the stay, and configured to ascend or descend along the stay; an elevation device mounted on the main frame and the stay, and configured to allow the main frame to ascend or descend along the stay; a rotating frame including a first end portion inserted into the stay and configured to ascend or descend along the stay, and a second end portion extending toward the rotation guide hole of the main frame; a rotating device mounted on the rotating frame and the rotation guide hole of the main frame, and configured to rotate the rotating frame along the rotation guide hole; and a headrest frame assembled to the rotating frame.