To provide a piping structure for a rainwater storage tank at a low cost by which foreign objects or dead leaves hardly block a passage of rainwater or the like, much labor is not needed for replacement of pipes and for maintenance, and a wall surface of a building gets only a few scratches.

An inner diameter of a short-pipe-like body of a water intake device used for piping of the rainwater storage tank is larger than an outer diameter of a drainage pipe to be connected. A front end part of the drainage pipe to be inserted into and connected to a drainage pipe connecting port is made to protrude to the inside of the short-pipe-like body. A space is formed between an inner peripheral surface of a lower part of the short-pipe-like body and an outer peripheral surface of a front end part of the drainage pipe. The rainwater flowing into the short-pipe-like body flows into the space. A height position of a bottom face of the space is made to be substantially the same as a height position of an inner face of a pipe bottom of an intake pipe connected to an intake pipe connection port.