To directly achieve cooling with a refrigerant gas, by fully increasing a heat transfer area and reducing the inner volume of a heat exchanger.

A capillary tube 1 has an inner diameter of 1.2 mm and an outer diameter of 2.0 mm, and a 5 m capillary tube 1 is set to 7.5 mm in radius at the center and is bent by 180° and is machined in an hair pin shape. The gap is set to 18 mm by a bottom spacer 2, and the upper part is connected to a refrigerant gas main header 5 with a diameter of 28 mm and a refrigerant liquid main header 6 via a refrigerant gas branch header 3 with a diameter of 12 mm and a refrigerant branch header 4. Both the branch headers are retained while maintaining an interval of 15.5 mm horizontally by another structure and is located at the apex of a regular triangle with its side being 18 mm in terms of top view in a zigzag arrangement. A heat transfer area is fully large and ice is thin, thus setting an evaporation temperature to 1.0°C or more below zero and improving the consumption efficiency of energy.