The present invention provides a preheater for vehicle, which comprises the following components: a PTC rod assembly; one or a plurality of radiating rib assemblies which are coupled to closely contact with two surfaces of each PTC rod assembly; a frame which is coupled to the outer surface of the utmost outside radiating rib assembly; and a first casing and a second casing which are provided with casing terminal and coupled to two combined longitudinal ends of each component; wherein each frame is formed bended to cause that these components can contact with each other closely. In the preheater according to the invention, heat generated by PTC component included in the preheater does not radiate outside but is only uniformly transferred to the radiating rib assembly. Furthermore close contact between the PTC rod assembly and the radiating rib assembly is improved.