A manufacturing device of the present invention includes an intermediate molded body mold having a first accommodating space capable of accommodating a plurality of preforms, each preform having a mouth portion and a trunk portion; an intermediate molded body blowing unit configured to blow gas into the plurality of preforms arranged in the first accommodating space to inflate the plurality of preforms, thereby manufacturing an intermediate molded body having a connection portion formed by the trunk portions of the plurality of preforms welded to each other; a final molded body mold having a second accommodating space larger than the first accommodating space; and a final molded body blowing unit configured to blow gas into the intermediate molded body arranged in the second accommodating space to inflate the intermediate molded body, thereby forming an exterior shape of a multiple-chamber container.