upper mold 402 is then moved down for clamping thus as shown in fig1 because the cavity is formed which is a space to fill a resin material for solidification by pouring injecting the resin material into the cavity from a pouring hole not shown and holding for a predetermined period of time the resin material is solidified and the first molded body 100 is insert molded to the bracket member 30 finally by press fitting the bushes into the press fitting holes of the bracket member 30 manufacturing of the vibration isolation device 1 is completed in this case because setting of the first molded body 100 to the lower mold 401 of the resin molding mold 400 is performed by inserting the resin lower mold pins 401 b into the holes 63 a bored in the second wall parts 63 of the external member 60 similarly to the case of the rubber vulcanizing step described above unless the orientation of the first molded body 100 that is the orientation of the external member 60 is correctly set and the resin lower mold pins 401 b corresponding to each of the respective holes 63 a are inserted respectively the first molded body 100 cannot be stored inside the cavity recess of the lower mold 401 accordingly even when the through hole 61 a of the external member 60 is formed in a deviated position and the first molded body 100 has directivity working failure installation failure in setting such first molded body 100 to the resin molding mold 400 can be surely suppressed also similarly to the case of the rubber vulcanizing step described above in a state the first molded body 100 is set to the lower mold 401 by.