portion 63 arranged between the condensing water supply tube 37 and the condensing tube 35 and interconnected for containing condensing water therein and an air tube 61 having one end connected to outside of the case 11 and the other end engaged in the container portion 63 so as to introduce condensing water in a dry processing without aeration from outside and so as to discharge the condensing water and then aerate when the dry processing is finished sectional areas of the lower region of the container portion 63 gradually decreases towards a down direction thereof also a supply opening 64 a is formed at an upper portion of the container portion 63 and connected with the condensing water supply tube 37 a drain hole 64 b is formed at a lower portion to discharge condensing water the drain hole 64 b is connected to a connecting tube 65 of which one end is connected to inside of the condensing tube 35 an aeration hole 64 c is formed above the drain hole 64 b for connecting the aeration tube 61 also a supply opening 64 d is formed above the aeration hole 64 c with a predetermined height difference so as to discharge condensing water to the condensing tube 35 region if a dry processing starts as shown in fig5 condensing water is supplied from the condensing water supply tube 37 to inside of the container portion 63 and some of the supplied condensing water is discharged into the condensing tube 35 through the drain hole 64 b and some is introduced into the aeration tube 61 so that aeration is not generated between inside of the tub 21 and outside thereby preventing air.