To provide an opening/closing remote device for a drain valve capable of easily draining waste water in a tank only by performing the lateral rotating operation of a handle.

In a drain mechanism constituted by connecting a drain pipe B to the lower side of a drain port A and the drain valve 1 vertically movable by remote operation to open/close the drain port A, the opening/closing remote device is composed of an operating mechanism, an expansion rod vertically expanded by the operation of the handle, and an operating part connected to the expansion rod. In the operating mechanism, a valve hole adjusting pipe 5 integrally supporting a valve cover support shaft 6 and a support shaft support frame 4 inside the drain pipe B is fittingly mounted in a vertically movable manner by thread adjustment, and a head part 9a of a lever piece 9 is engaged into a groove hole 4a of a support shaft operating pipe 3 to vertically operate the support shaft operating pipe 3 and the whole valve hole adjusting pipe 5 at the same time to adjust a clearance of the drain port. Both ends of a wire are interlockingly connected to the expansion rod and the lever piece 9 to open/close while adjusting the clearance of the drain valve 1 and drain port A by the operation of the handle.