To provide a manufacturing method for a synthetic resin hollow structure, which is simpler than its conventional method by contriving the improvement of workability and the elimination of processes, and at the same time, manufacture the synthetic resin hollow structure having no through mark of a compressed air introducing nozzle.

By piercing a compressed air introducing nozzle 9 equipped with the product forming cavity 11 of upper and lower molds B1 and B2 or a sub-chamber forming part provided adjacent to the cavity in a sheet 2 so as to introduce compressed air between sheets 1 and 2 under the condition that the two thermoplastic synthetic resin sheets 1 and 2, between which a separator 3 is inserted to be pinched, are pinched between the upper and the lower molds B1 and B2, the sheets are brought into close contact with the inner surface of the cavity 11 and, in addition, the sheet piercing with the nozzle 9 is carried out under the condition that the sheets are attracted under vacuum to the mold B2 having the nozzle.