To provide a waterproof plate device capable of improving certainty of an operation of a waterproof plate and a degree of freedom in control of the waterproof plate.

A waterproof plate device includes: a waterproof plate 17 configured to be able to ascend from the surface of a road to dam water; a groove-shaped waterproof plate housing pit 14 formed to be able to house the waterproof plate; a groove-shaped water collection pit 13 formed to allow water to flow therein when flooded; a water-collecting bucket 16 which is a vessel arranged in the water collection pit, storing water flowing into the water collection pit, and formed to be able to move down in the water collection pit; and a transfer mechanism 31 connecting the waterproof plate and the water-collecting bucket with each other and converting a force of the descending water-collecting bucket into a force of the ascending waterproof plate. The transfer mechanism is provided with waterproof plate ascending prohibition means 41, 43c and switching means 44 for switching between a state for prohibiting the ascending of the waterproof plate and a state for permitting the ascending of the waterproof plate.