PURPOSE: To provide a method for bending metallic tube, which prevents burning flaws causing in a contact part between a plug and the inside surface of a tube and preventing the vibration of a mandrel connected to the plug by the use of a simply structured device.

CONSTITUTION: The method is for bending a straight metallic tube into a curved tube; a mandrel 3 with a plug 2 attached at the tip end is inserted into the rear end of a metallic tube 1; and a bending is performed while a lube oil is supplied through the mandrel 3 to a contact part between the plug 2 and the tube 1.