PURPOSE: To dry a paper tube quickly by microwave projection, by a method wherein the paper tube coated with adhesive agent and formed into a predetermined configuration is transferred by a belt conveyer while a drying chamber equipped with a microwave oscillator is provided on the transfer passage.

CONSTITUTION: A paper tube 11 coated with adhesive agent and formed into a predetermined configuration is transferred by a belt conveyer 12. A drying chamber 14 is provided on the transfer passage and a microwave oscillator 15, an isolator 16, a wave guide 17, a stirer 18 and an air discharging fan 19 are provided. The microwave oscillator 15 is operated stably by the isolator 16, the microwave is guided to a projecting unit through the wave guide 17 and is projected against a part to be projected uniformly through the stirer 18. The inner and outer surfaces of the paper tube 11 are heated and dried uniformly within a short period of time while heat inertia is discharged to the outside of the system by the fan 19.