PURPOSE: To satisfactorily suppress a fact that peeling is generated between a base metal pipe and a cladding pipe which are clod against each other, and also, to suppress the crack by forming successively a large diameter part in which a contact line to a cladding pipe stock is roughly parallel to the axis of a core material, an escape part in which the contact line is separated gradually, and a small diameter part in which the contact line is roughly parallel.

CONSTITUTION: A negative convergence angle α is given to a rolling roll 1, and also, a bite part 1a is separated gradually toward the entry and contact length to a cladding pipe stock 20 is secured long, therefore, pushing force of the cladding pipe stock 20 is obtained strongly. The cladding pipe stock 20 passes through a wall thickness rolling reduction part 1b and is rolled, reaches a large diameter part 1e of a rolling part 1c and is subjected to rolling reduction sufficiently, and a base metal pipe and a cladding metal pipe are pressed against each other. In that case, the cladding pipe stock 20 expands in the axial direction, and also, an expanding deformation in the peripheral direction is generated. Subsequently, it is subjected to reduction shaping by passing through successively the rolling part 1c, that is, a parge diameter part 1e, an escape part 1f and a small diameter part 1g, and a clad pipe 2 subjected to rolling is fed out of a relief part 1d.