a first cultivating farm that is filled with water and makes it possible to cultivate marsh snails and a second cultivating farm that is partitioned in the first cultivating farm as water can be circulated between the first and second cultivating farms and fishes are raised, in which the marsh snails that inhabit in the first cultivating farm are cultivated by eating excretions that are excreted from the fishes that inhabit in the second cultivating farm as food. (Representative drawing