Disclosed herein a technique for producing a gas mixture for controlling an oxygen concentration in the interior of a container while reducing the overall weight of the apparatus. For this purpose, a gas mixture supply device is provided for a container refrigeration apparatus. The gas mixture supply device is provided with adsorption columns (34, 35). If one of the first and second adsorption columns (34) and (35) is supplied with air, the adsorption columns (34, 35) are pressurized, and nitrogen in the air is adsorbed onto an adsorbent. If air is sucked from the other of the first and second adsorption columns (34) and (35), the adsorption columns (34, 35) are depressurized, and nitrogen adsorbed onto the adsorbent is desorbed. A gas mixture including the nitrogen desorbed from the adsorbent is supplied to the interior of a container (11).
