To provide a method for manufacturing an aluminum tube which prevents the corrosion of the circumferential face inside the mouth.

In an aluminum tube wherein an undercut section X for fitting an inner stopper body 7 into the mouth 2 of the aluminum tube 1 is formed, an expanded section 2a and a curved section 4 are formed at the mouth before being formed, in anticipation of the shift amount due to forming so that, in forming the undercut section X by touching a form rolling die 3 to the outer circumferential face of the mouth 2, the inner circumferential face of the mouth expanded inwardly by the pressure of the form rolling die 3 becomes evenly and smoothly continuous with other inner circumferential face. This manufacturing method is capable of manufacturing an excellent aluminum tube of a low ERV value (energizing value) which has no adverse effect of form rolling on the inner circumferential face of the mouth 2.