To improve heating efficiency of air-fuel mixture supplied from a carbureter and to efficiently vaporize liquid fuel in a non-vaporized state.

This device is constituted to be furnished with a heat insulator 7 arranged between a carbureter to generate air-fuel mixture and an air intake pipe 2 connected to an engine 3, a heat radiating plate set in a through hole formed on a central part of this heat insulator 7, a heating element to heat the heat radiating plate by making contact with the heat radiating plate and an electrode to electrify the heating element from outside through the heat radiating plate. In this case, at least two sets each of the heat radiating plates and the heating elements are provided, each set of the heat radiating plates 11a, 11b is arranged along a flow of the air-fuel mixture, and each set of the heating elements 15a, 15b is arranged in the neighbourhood of the heat insulator 7 and on the downstream side in the air intake pipe 2. Thereafter, an upper part region of each of the heat radiating plates 11a, 11b is made contact with the one heating element 15a in the neighbourhood of the heat insulator 7, and a lower part region of each of the heat radiating plates 11a, 11b is made contact with the other heating element 15b on the downstream side.