To provide an efficiently operated carburetor by forming fins of a finned pipe with intermittently disposed cutouts in the longitudinal direction.

Fins 22 of finned pipes standing close together are provided with cutouts 23 at fixed spaces in the longitudinal direction. The dimensions of the cutouts 23 are determined in consideration of a ventilating effect and a heat absorbing effect of the fins 22 (Fig. (a)). It is understood that the finned pipes stand close together (Fig. (b)). By thus providing cutouts in the fins of the finned pipe 21, air can be circulated in any direction of arrows X, Y, Z through the cutouts 23 so that heat of vaporization can be enough absorbed. The finned pipes 21 standing close together are installed at a gradient, whereby some of sucked air strikes against the end of the cutout 23 of the fin 22 as indicated by arrows to make a divided flow, and the flow is changed axially, so that the efficiency of absorbing heat of vaporization can be further improved.