Provided is a water blocking board apparatus which can improve reliability of the operation of a water blocking board, the apparatus having: a water blocking board 16 configured to ascend from a road surface to block water to prevent water from entering a building etc. from a passage; a water blocking board accommodating pit 14 in a groove shape formed under the road surface so as to accommodate the water blocking board; a water collecting pit 13 in a groove shape arranged in a passage where the water blocking board accommodating pit is formed, and configured to allow water to flow thereinto upon flooding; a water collecting bucket 15 being a container disposed in the water collecting pit to accumulate water having flown into the water collecting pit and configured to descend in the water collecting pit by a weight of the water accumulated in the water collecting bucket; and a transmission mechanism 31 which connects the water blocking board and the water collecting bucket with each other directly or via another component and converts a force for the water collecting bucket to descend into a force for the water blocking board to ascend, wherein at least one of the transmission mechanism and the water collecting bucket is provided with a device 40 for inhibiting inclination of the water collecting bucket.