Abstract: The invention relates to an apparatus for cooling a plurality of preforms made of thermoplastic material which continuously move on a conveyor belt. The apparatus includes a cylindrical casing with a vertical extension formed by two coaxial cylinders, such a casing contains a guide crossed by a chain or a cable for transporting the preforms therein. The guide, which forms a closed path, comprises a first helical stretch, which raises from the lower plane starting from a station in which the preforms coming from a conveying device are hooked by the chain or by the cable, a second straight stretch, which returns the preforms to the lower plane once they have reached the upper plane, and a third flat stretch at the height of the lower plane, which returns the preforms to the arrival station. The helical stretch of the guide is contained within a cooling tunnel formed in the gap between the two walls of the outer cylinder and the inner cylinder of said casing.