PURPOSE: To easily pull out a core body by a method wherein a covered core body is taken up during a period when the core body is held to definite temp. while air is introduced into the interface of cover material and the core body under pressure from the terminal of the covered core body and the air introduced under pressure between the taken-up part and the seal end part of the cover material is allowed to successively flow to form a clearance to the interface.

CONSTITUTION: A tubular cover material is extruded on a core body 10 to cover the same to form a covered core body 10a and vulcanized on the core body by a vulcanizing cylinder 3 to store the diameter of the cover material. Subsequently, the cover material is cooled by a cooling cylinder 4 and the cooled end thereof is sealed and, during a period when the core body 1 is held to a definite temp., the covered core body 10a is taken up while air is introduced into the interface of the cover material and the core body 10 under pressure from the terminal of the covered core body and the air introduced under pressure between the taken-up part 8 and the sealed part is successively moved to continuously form a clearance to the interface. By this method, the core body 10 can be easily pulled out while dimensional accuracy is stabilized.