PURPOSE: To prevent water leakage due to fatigue-breakage of a draining part, by fitting a straight pipe to the periphery of a hole on the bottom plate of a cabinet body and inserting the lower part of straight pipe into the upper end of a sewage pipe and inserting the drain pipe of a water tank into the end of the straight pipe.

CONSTITUTION: A hole 9 is opened on the bottom plate 8 of a vertically movable cabinet body and a straight pipe 11 is fitted to the periphery of the hole through a holder 10. The lower part of the pipe 11 is inserted so as to be freely raised and lowered into the rising pipe 12 of a sewage pipe 20 arranged under the bottom plate 8 and the lower end of a flexible drain pipe 14 connected to a drain metal tool 13 attached to the drain outlet of the water tank is inserted in the upper end of the pipe 11. Respective clearances between the pipe 11 and the rising pipe 12 and the drain pipe 14 are sealed with sealing members 17A, 17B. When the cabinet body is raised or lowered, the pipe 11 is moved to slide along the rising pipe 12 while keeping the connected condition between the pipe 11 and the drain pipe 14 to prevent water leakage due to fatigue- breakage resulting from the extending and contracting motion.