PURPOSE: To provide a clad tube capable of withstanding the accelerated corrosion, and capable of effectively preventing breakage of the clad by the interactive effect between pellets and the clad, and a method to manufacture the clad tube.

CONSTITUTION: A clad tube 17 comprises an outer circumferential base layer 21 made of Zircaloy, a depletion region 25 extending from an inner surface of the outer circumferential base layer 21 to its inside, and a zirconium barrier layer 22 to be joined with the inner surface of the outer circumferential base layer 21. The depletion region 25 contains the alloy element of the substantially lower concentration than the concentration of the alloy element in a base layer region outside thereof. Diffusion annealing is performed at the end of the method to manufacture the clad tube of this constitution. Because a part of the alloy element is transferred from the depletion region 25 into the zirconium barrier layer 22, the barrier layer 22 can withstand the accelerated corrosion. In addition, the depletion region 25 is higher in adaptability than the other region of the base layer 21, contributing to solution of the problem of the interactive effect between pellets and the clad.