A locking drain device for a floor drain comprises a top strainer, a cylindrical middle section having spreadable sides with slits in them, a frustoconical spreader, and a locking bolt, such that, when the spreader is drawn against the spreadable sides of the cylindrical middle section by tightening the locking bolt, the cylindrical sides will be spread to frictionally engage against the internal surface of a drain pipe to prevent inadvertent removal of the floor drain.