Global climate change has led to an increase in the frequency and the intensity of heavy rainfall events. As a result, flooding has become more frequent in recent years. In Japan, the concept of “green infrastructure” has been introduced as a countermeasure, and measures to actually put it into operation have been in motion since 2013. Green infrastructure for flood control is mainly installed in administrative facilities such as public parks, and most of them are small scale. Based on the principle of flood control in a river basin, we believe that flood control functions should be introduced to large-scale private facilities that have not yet been utilized as green infrastructure. In this study, we focused on green spaces of large-scale factories, which are required by the Factory Location Law to have a certain scale of green space. Also, we proposed that the land should be used as a storage and infiltration facility, and examined the effectiveness of such a facility. The results showed that the effect was comparable to that of the existing flood control reservoirs.