To reduce the accumulation of salts and the emergence of alga in a bottom watering apparatus.

This bottom watering apparatus comprises plural long grooves 12 which are roughly parallelly placed with a specific interval, waterways 14 formed on partitions 13 separating adjacent two long grooves 12 in such a manner that the waterway is connected to each of the adjacent long grooves 12 which are adjacent to each other having a partition 13 between themselves, and water retaining materials 20. The water retaining materials are placed on the long grooves 12, respectively, and they can support culturing medium materials on which plants are planted. By this structure, the ratio of the area of the water retaining material 20 to the board-shaped member 10, on which the long grooves 12 are formed, is smaller than the conventional case, and when the culturing medium material 30 is placed, the water retaining material does not touch the culturing medium material, and the area of the part which is exposed to air is small, and thereby the accumulation of salts and the emergence of alga are reduced.