The execution of rainwater utilization system was examined for station toilets with the many user numbers per instrument. The following were set on the past investigation value and Tokyo JR 5 stations using opened data' Precipitation, rainwater collection plane, toilet water consumption and rainwater tank. Afterwards, the usefulness of rainwater utilization system was examined by the simulation. Though as the result, the effect of the rain water tank installation is accepted, the toilet water consumption for one day is large, the range of 136 m^3 from 55 m^3. Hence, it seems to be the difficulty that the space for the even one day tank is newly installed in the station premise. Moreover, by the simulation method, it was shown to be sufficiently effective for station toilets by the system with the capacity for the maximum water consumption per one hour, using the rainwater without storing that almost.
