To cause storage rainwater which overflows to seep into the ground and to provide a reservoir in which aquatic animals and plants grow, for a rainwater storage and utilizing system whereby rainwater falling on the whole site of a house is used in everyday life water.

A rainwater storage tank whereby rainwater falling on the roof of a house is stored for use in everyday life is placed within a housing site below the roof, and a reservoir L guiding water overflowing from the rainwater storage tank or water stored therein is provided to purify the water overflowing from the reservoir L and to cause the water to seep into the ground. A fountain pump P2 is placed within the reservoir L, and a fountain 3 where the storage water is discharged from the fountain pump P2 and purified through aeration is placed. A plant sanctuary U around a pond is placed adjacent to the reservoir L.