A method for manufacturing a double pipe includes: drawing a plate (1), which has a predetermined shape corresponding to the desired final shape of a curved outer pipe (4), into a curved, substantially U-shape in cross-section to produce a half pipe (2). Then, an inner pipe (3), which has a curved shape similar to the desired final curved shape of the outer pipe, is inserted into and positioned within the interior space of the half pipe. Subsequently, the inner pipe is welded to the half pipe at one longitudinal end thereof. Thereafter, longitudinally-extending edges of the half pipe are curled towards each other until they abut and a substantially circular cross-section is formed that surrounds the exterior of the inner pipe. The abutting longitudinally-extending edges (22) of the half pipe are then welded together to produce the curved outer pipe (4).