PURPOSE: To enable manufacture of an elbow without causing deformation in manufacturing an elbow from a metallic tube by filling a material made up of metallic grains and fine heat resisting sand having greater coefficient of thermal expansion than that of the metallic tube in whole bending part of the metallic tube.

CONSTITUTION: In manufacturing an elbow from a tube 1 made of material having large cold brittleness such as carbon steel, outer diameter central bending part 11 of the tube is increased from both ends toward the center and inner diameter is made uniform throughout. Powdery material 2 made by mixing grains of austenite stainless steel etc. which is greater in coefficient of thermal expansion than carbon steel and river sand, fine heat resisting sand etc. in volume ratio of 3:1 is filled in the tube. Stoppers 13, 13' are welded on both ends of the tube 1 and an air vent 13a' is provided in the stopper of one side. This is heated to about 1,000°C and bend to an elbow by a bending device. By this way, the tube can be bent to an elbow without causing defects in shape such as V-shaped fold, buckling, flattening, reduction etc.