external air flows into the refrigerating and freezing compartments 3 a and 3 b at this time the air in the refrigerating and freezing compartments 3 a and 3 b is contracted thereby causing a change in pressure of the storage compartments 3 a and 3 b due to this change the open close member 40 of the drain valve 30 moves upward as illustrated in fig6 and 7 the air flowing port 33 of the valve body 35 is opened by upward movement of the open close member 40 that has closed the air flowing port 33 and external air flows inside the valve body 35 through the air flowing port 33 the air which flows inside the valve body 35 flows into the drain pipe 23 through the passing hole 42 and the defrost water flowing hole 32 of the open close member 40 the air flown into the drain pipe 23 continuously moves upward and flows inside the refrigerating and freezing compartments 3 a and 3 b thereby settling the change in pressure of the storage compartments 3 a and 3 b thus the doors 7 a and 7 b can be easily opened with a little force after the change in pressure of the storage compartments 3.