A heating element cover component includes a hollow outer shell portion of a required length, having required rigidity and thermal conductivity, a substantially half-pipe shaped abutting portion formed with a required thickness on the outside of the outer shell portion in a longitudinal direction of the outer shell portion, having flexibility and thermal conductivity, and with a slit penetrating in a thickness direction formed over the entire length in the longitudinal direction, a connecting portion having flexibility and thermal conductivity, connecting opposed edges of the abutting portion in the longitudinal direction with the outer shell portion, and an engaging portion constituted with a projecting piece and a projecting piece inserting portion being engaging elements disposed at line-symmetrical positions using a longitudinal straight line located at a widthwise middle of the abutting portion as an axis of symmetry to form a pair structured to be engageable with each other.