Provided is an opening crystallisation device which, even when crystallising a molded article opening having a large aperture, limits an increase in the long side/short side ratio of a machine base, reduces the bending of endless members such as chains, and can increase conveyance speed and increase throughput. An opening crystallisation device has a rectangular machine base (20) having a long side and a short side in planar view, a plurality of sprockets (30-34) arranged in the machine base, and an endless member (35) which passes over each of the sprockets. A conveyance path (40), formed in the region wherein the endless member is arranged, extends along the direction of the long side, includes parallel first-fourth linear conveyance paths (41-44) wherein two conveyance directions which are adjacent in the short-side direction are opposite to one another, and is provided with: a plurality of heating units (50) which are arranged at least along the first-third linear conveyance paths and which heat an opening; a cooling unit (60) which is arranged at least along the fourth linear conveyance path and which cools the opening; a molded article supply unit (70) which is upstream of the heating units and which supplies a molded article; and a molded article extraction unit (80) which extracts the molded article between the cooling unit and the molded article supply unit.