To provide a mandrel for producing a rubber hose which can be applied to a usual rubber hose with a reinforcing layer constituted by braiding reinforcing threads of organic fibers and can heat the rubber hose from its inside.

The resin metal composite mandrel 10 is constituted by embedding a low melting point metal 14 whose melting point is 200°C or below and lower than the melting point of the resin continuously in the axial direction in a mandrel main body 12 of the resin. An unvulcanized rubber hose which is extrusion-molded while coating the periphery of the mandrel 10 is heated from the inner surface side by heating the low melting temperature metal 14 of the mandrel 10 by high frequency induction heating.