PURPOSE: To form a rubber bag and rubber tubes integrally so as to reduce the number of steps of molding a rubber bag for a sphygmomanometer arm belt, by using a rubber bag mold having rubber tube forming cores connected thereto, and dipping the rubber bag mold in a latex rubber.

CONSTITUTION: The rubber bag mold 1 has the rubber tube cores 2 at a connecting section 2' projected partially form the outer periphery thereof. Then the rubber bag mold except part of a lug 1' is dipped into a latex 6 in a tank 5 with the rubber tube cores 2 down so that a required thickness of the latex is allowed to adhere to the rubber bag mold 1. Then, the rubber bag mold 1 is raised to such a level that the tip of the connecting section 2' of the rubber tube cores 2 is still dipped in the latex so that the downflow of the latex is stabilized and the rubber tube sections 4 is remained in the latex to be dipped therein. Thus the mold is taken out from the latex with only the rubber tube sections 4 having an increased thickness of the latex followed by drying so that the rubber bag 3 and rubber pipe sections 4 are integrally molded.