To prevent the floating of a duckboard for a drain ditch by boring multiple through holes on a top plate section.

Multiple through holes 111 are bored at fixed intervals on the top plate section 11 of a duckboard material 1 made of a rigid vinyl chloride resin, and leg plate sections 12 are suspended from both end sections of the top plate section 11. Multiple duckboard materials 1 are arranged at fixed intervals and connected by multiple connection plate sections 2. Lock plate sections 21 are suspended below both ends of the connection plate sections 2 to form a duckboard for a drain ditch. The lock plate sections 21 are locked on the ditch provided on the washing place floor of a bathroom to install the duckboard. Even when a large quantity of hot water overflows into the ditch, the air below the top plate sections 11 of the duckboard materials 1 is discharged from the through holes 111, no air is sealed below the top plate sections 11, thereby the floating of the duckboard can be prevented.