A heater for a motor vehicle comprising: a heat source part; a heat source part rod including a rod sidewall configured to receive the heat source part; a first heat radiating plate including a first heat generation region and a first air movement region, the first air movement region having at least one first through-hole formed therein; and a second heat radiating plate including a second heat generation region and a second air movement region, the second air movement region having at least one second through-hole formed therein, wherein the heat source part is disposed between the first heat radiating plate and the second heat radiating plate, and the rod sidewall is provided integrally with the first heat radiating plate, characterized in that the heat source part includes a positive temperature coefficient device, an electrode plate electrically contacting the positive temperature coefficient device, and insulating guide members (160, 160') insulating the positive temperature coefficient device and the electrode plate from the rod sidewall, wherein the second heat radiating plate is provided with a plurality of fastening grooves (560a and 560b), wherein the rod sidewall is a second rod sidewall including a pair of second sidewalls spaced apart from each other by a predetermined distance so as to define a predetermined space between said second sidewalls, and at least one second modified part extended to penetrate through the fastening grooves (560a and 560b) and pressed to an upper surface of the second heat radiating plate to thereby be bent and caulking-coupled to the upper surface of the second heat radiating plate, and wherein said heat source part, with its insulating guide members (160, 160') is seated on the predetermined space disposed between said second sidewalls. a heat source part; a heat source part rod including a rod sidewall configured to receive the heat source part; a first heat radiating plate including a first heat generation region and a first air movement region, the first air movement region having at least one first through-hole formed therein; and a second heat radiating plate including a second heat generation region and a second air movement region, the second air movement region having at least one second through-hole formed therein, wherein the heat source part is disposed between the first heat radiating plate and the second heat radiating plate, and the rod sidewall is provided integrally with the first heat radiating plate, characterized in that the heat source part includes a positive temperature coefficient device, an electrode plate electrically contacting the positive temperature coefficient device, and insulating guide members (160, 160') insulating the positive temperature coefficient device and the electrode plate from the rod sidewall, wherein the second heat radiating plate is provided with a plurality of fastening grooves (560a and 560b), wherein the rod sidewall is a second rod sidewall including a pair of second sidewalls spaced apart from each other by a predetermined distance so as to define a predetermined space between said second sidewalls, and at least one second modified part extended to penetrate through the fastening grooves (560a and 560b) and pressed to an upper surface of the second heat radiating plate to thereby be bent and caulking-coupled to the upper surface of the second heat radiating plate, and wherein said heat source part, with its insulating guide members (160, 160') is seated on the predetermined space disposed between said second sidewalls.