A bathroom floor panel for use in an airtight and water tight space is configured to be efficiently dried in a few hours under ambient conditions. When water drops onto the floor panel, the surface tension of the water is broken by irregular-shaped portions and the water spreads without forming waterdrops. Also, the irregular-shaped portions reduce the flow velocity of the water due to a gradient of the panel, so as to prevent the water flowing in channels to a drain from being discontinued. With this, although the drain velocity of the water is low, substantially no water remains as isolated drops. Further, even if some water remain on the irregular-shaped portions after the water flows out the channels to the drain, any amount of water remaining in the channels is evaporated in a relatively short period of time because the amount of the remaining water is very small.