PURPOSE: To heat a can body uniformly to the prescribed distance on both sides of the seam thereof to a prescribed temp. by symmetrically disposing an injection nozzle with the vertical surface running the center line of a burner and forming slits between the vertical surfaces of longitudinals and the surface of in intermediate plate.

CONSTITUTION: The hot air injection nozzle 3 of a device for baking a belt-like coated film to the welded seam of the can body has a pair of the longitudinals 4a, 4b arranged symmetrical with the vertical plane 7 passing the center line 14 of the burner 2. The longitudinals 4a, 4b respectively have the vertical surfaces 6a, 6b spaced by the prescribed distance from the vertical plane 7. The vertical belt-like intermediate plate 5 is inserted into the space 20 thereof. The slits S1, S2 are formed between the vertical surfaces 7 of the longitudinals and the plate 5. The can body is thus heated to the prescribed temp. and to the prescribed distance in the circumferential direction on both sides of the welded seam by the nozzle having two lines of the slits, by which the coated film is thoroughly cured.