To attain a heating effect with extremely small power consumption in an extremely short time by concentrically arranging a flexible electric heater at the portion of a seat kept in contact with the human body in a vehicle.

A thin film heater 1 closely stuck with a polyimide resin film 2 is pinched by silicone rubber sheets 5 with high insulation to form a heater unit H, for example. The heater unit H is pinched by a sponge protective fabric at the bottom section and a flannel texture fabric as a surface protective fabric at the upper section, they are stuck by silicone rubber at the prescribed positions, a rayon texture fabric is arranged as a back protective fabric at the lower section, and it is integrated with a silicone rubber seat to form a heating device for a seat. The flexible heater unit H extracted with lead wires 4 from terminals 3 is buried in the cover of the seat of a motorcycle, and it is fed with electric power from the battery of the motorcycle. A heating section is arranged only at the portion of the seat of the motorcycle to be kept in contact with the hips, heat is transferred to the whole body from the hips, and wasteful power consumption due to heat radiation when the heating section is exposed to wind can be prevented.