PURPOSE: To prevent outside rubber from generating swelling or defective adhesion, by making use of a cap where a plurality of through holes communicating with the outside through an inside part of the cap against which a fiber reinforcing layer exposed to a section of an end part of an unvulcanized rubber hose abuts are formed.

CONSTITUTION: A plurality of through holes 9 communicating with the outside through an inside part of a cap against which a fiber reinforcing layer 3 exposed to a section 10 of an end part of an unvulcanized rubber hose 1 are formed in the cap 6 to be fitted to control the section 10 of the end part of the unvulcanized rubber hose 1 and an external circumferen tial surface. Therefore, even if a bath liquid or air or water remains behind in the fiber reinforcing layer 3, the same arrives at the section 10 of the end part of the unvulcanized rubber hose 1 by passing through a fine gap of the fiber reinforcing layer 3 while the same is apt to evaporate or expand by being heated at a high temperature at the time of vulcaniza tion and the same can be fled outside through a plurality of the through holes 9 of the cap 6 further. Even if the bath liquid or the air or the water is shut up in a space between the inside and outside rubber 2, 4, since the same is fled through the through holes 9 and does not stay under a state of bubbles, swelling or defective adhesion of the outside rubber 4 can be eliminated.