PURPOSE: To obtain the mandrel excellent in durability and flexibility by covering closely the outer periphery of the rubber mandrel in which a rubber layer is provided at the periphery of a core body made of a steel wire cord with the thin sheet layer made of specified thermoplastic resin.

CONSTITUTION: In a flexible mandrel 6, a rubber layer 5 is provided outside the core body 4 made of a steel wire cord, and its outer periphery is covered with a resin thin sheet 7. The outside of the flexible mandrel 6 is covered with the rubber hose 2 with an inner rubber 3. In this case, the resin sheet 7 has the thickness equal to or less than a quarter of the rubber mandrel 6-diameter, and made of the thermoplastic resin having melting point equal to or higher than 150°C, whereby there is no interaction between the outer periphery of the mandrel and the inner rubber of the hose. The mandrel has long life and is applicable to a large diameter rubber hose due to its superior flexibility.